content/browser/loader/resource_scheduler_unittest.cc

// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "content/browser/loader/resource_scheduler.h"

#include <memory>
#include <utility>
#include <vector>

#include "base/memory/ptr_util.h"
#include "base/metrics/field_trial.h"
#include "base/metrics/field_trial_param_associator.h"
#include "base/run_loop.h"
#include "base/strings/string_number_conversions.h"
#include "base/test/histogram_tester.h"
#include "base/test/mock_entropy_provider.h"
#include "base/test/scoped_feature_list.h"
#include "base/timer/mock_timer.h"
#include "base/timer/timer.h"
#include "content/public/browser/resource_context.h"
#include "content/public/browser/resource_throttle.h"
#include "content/public/test/mock_render_process_host.h"
#include "content/public/test/test_browser_context.h"
#include "content/public/test/test_browser_thread_bundle.h"
#include "content/test/test_render_view_host_factory.h"
#include "content/test/test_web_contents.h"
#include "net/base/host_port_pair.h"
#include "net/base/request_priority.h"
#include "net/http/http_server_properties_impl.h"
#include "net/traffic_annotation/network_traffic_annotation_test_helper.h"
#include "net/url_request/url_request.h"
#include "net/url_request/url_request_test_util.h"
#include "testing/gmock/include/gmock/gmock.h"
#include "testing/gtest/include/gtest/gtest.h"
#include "ui/latency/latency_info.h"
#include "url/scheme_host_port.h"

using std::string;

namespace content {

namespace {

class TestRequestFactory;

const int kChildId = 30;
const int kRouteId = 75;
const int kChildId2 = 43;
const int kRouteId2 = 67;
const int kBackgroundChildId = 35;
const int kBackgroundRouteId = 43;

const char kPrioritySupportedRequestsDelayable[] =
    "PrioritySupportedRequestsDelayable";

const char kNetworkSchedulerYielding[] = "NetworkSchedulerYielding";
const int kMaxRequestsBeforeYielding = 5;  // sync with .cc.

class TestRequest : public ResourceThrottle::Delegate {
 public:
  TestRequest(std::unique_ptr<net::URLRequest> url_request,
              std::unique_ptr<ResourceThrottle> throttle,
              ResourceScheduler* scheduler)
      : started_(false),
        url_request_(std::move(url_request)),
        throttle_(std::move(throttle)),
        scheduler_(scheduler) {
    throttle_->set_delegate_for_testing(this);
  }
  ~TestRequest() override {
    // The URLRequest must still be valid when the ScheduledResourceRequest is
    // destroyed, so that it can unregister itself.
    throttle_.reset();
  }

  bool started() const { return started_; }

  void Start() {
    bool deferred = false;
    throttle_->WillStartRequest(&deferred);
    started_ = !deferred;
  }

  void ChangePriority(net::RequestPriority new_priority, int intra_priority) {
    scheduler_->ReprioritizeRequest(url_request_.get(), new_priority,
                                    intra_priority);
  }

  void Cancel() override {
    // Alert the scheduler that the request can be deleted.
    throttle_.reset();
  }

  const net::URLRequest* url_request() const { return url_request_.get(); }

 protected:
  // ResourceThrottle::Delegate interface:
  void CancelAndIgnore() override {}
  void CancelWithError(int error_code) override {}
  void Resume() override { started_ = true; }

 private:
  bool started_;
  std::unique_ptr<net::URLRequest> url_request_;
  std::unique_ptr<ResourceThrottle> throttle_;
  ResourceScheduler* scheduler_;
};

class CancelingTestRequest : public TestRequest {
 public:
  CancelingTestRequest(std::unique_ptr<net::URLRequest> url_request,
                       std::unique_ptr<ResourceThrottle> throttle,
                       ResourceScheduler* scheduler)
      : TestRequest(std::move(url_request), std::move(throttle), scheduler) {}

  void set_request_to_cancel(std::unique_ptr<TestRequest> request_to_cancel) {
    request_to_cancel_ = std::move(request_to_cancel);
  }

 private:
  void Resume() override {
    TestRequest::Resume();
    request_to_cancel_.reset();
  }

  std::unique_ptr<TestRequest> request_to_cancel_;
};

class FakeResourceContext : public ResourceContext {
 private:
  net::HostResolver* GetHostResolver() override { return NULL; }
  net::URLRequestContext* GetRequestContext() override { return NULL; }
};

class ResourceSchedulerTest : public testing::Test {
 protected:
  ResourceSchedulerTest() {
    InitializeScheduler();
    context_.set_http_server_properties(&http_server_properties_);
  }

  ~ResourceSchedulerTest() override {
    CleanupScheduler();
  }

  // Done separately from construction to allow for modification of command
  // line flags in tests.
  void InitializeScheduler() {
    CleanupScheduler();

    // Destroys previous scheduler, also destroys any previously created
    // mock_timer_.
    scheduler_.reset(new ResourceScheduler());

    scheduler_->OnClientCreated(kChildId, kRouteId);
    scheduler_->OnClientCreated(
        kBackgroundChildId, kBackgroundRouteId);
  }

  void CleanupScheduler() {
    if (scheduler_) {
      scheduler_->OnClientDeleted(kChildId, kRouteId);
      scheduler_->OnClientDeleted(kBackgroundChildId, kBackgroundRouteId);
    }
  }

  std::unique_ptr<net::URLRequest> NewURLRequestWithChildAndRoute(
      const char* url,
      net::RequestPriority priority,
      int child_id,
      int route_id) {
    std::unique_ptr<net::URLRequest> url_request(context_.CreateRequest(
        GURL(url), priority, NULL, TRAFFIC_ANNOTATION_FOR_TESTS));
    return url_request;
  }

  std::unique_ptr<net::URLRequest> NewURLRequest(
      const char* url,
      net::RequestPriority priority) {
    return NewURLRequestWithChildAndRoute(url, priority, kChildId, kRouteId);
  }

  std::unique_ptr<TestRequest> NewRequestWithRoute(
      const char* url,
      net::RequestPriority priority,
      int route_id) {
    return NewRequestWithChildAndRoute(url, priority, kChildId, route_id);
  }

  std::unique_ptr<TestRequest> NewRequestWithChildAndRoute(
      const char* url,
      net::RequestPriority priority,
      int child_id,
      int route_id) {
    return GetNewTestRequest(url, priority, child_id, route_id, true);
  }

  std::unique_ptr<TestRequest> NewRequest(const char* url,
                                          net::RequestPriority priority) {
    return NewRequestWithChildAndRoute(url, priority, kChildId, kRouteId);
  }

  std::unique_ptr<TestRequest> NewBackgroundRequest(
      const char* url,
      net::RequestPriority priority) {
    return NewRequestWithChildAndRoute(
        url, priority, kBackgroundChildId, kBackgroundRouteId);
  }

  std::unique_ptr<TestRequest> NewSyncRequest(const char* url,
                                              net::RequestPriority priority) {
    return NewSyncRequestWithChildAndRoute(url, priority, kChildId, kRouteId);
  }

  std::unique_ptr<TestRequest> NewBackgroundSyncRequest(
      const char* url,
      net::RequestPriority priority) {
    return NewSyncRequestWithChildAndRoute(
        url, priority, kBackgroundChildId, kBackgroundRouteId);
  }

  std::unique_ptr<TestRequest> NewSyncRequestWithChildAndRoute(
      const char* url,
      net::RequestPriority priority,
      int child_id,
      int route_id) {
    return GetNewTestRequest(url, priority, child_id, route_id, false);
  }

  std::unique_ptr<TestRequest> GetNewTestRequest(const char* url,
                                                 net::RequestPriority priority,
                                                 int child_id,
                                                 int route_id,
                                                 bool is_async) {
    std::unique_ptr<net::URLRequest> url_request(
        NewURLRequestWithChildAndRoute(url, priority, child_id, route_id));
    std::unique_ptr<ResourceThrottle> throttle(scheduler_->ScheduleRequest(
        child_id, route_id, is_async, url_request.get()));
    auto request = base::MakeUnique<TestRequest>(
        std::move(url_request), std::move(throttle), scheduler());
    request->Start();
    return request;
  }

  void ChangeRequestPriority(TestRequest* request,
                             net::RequestPriority new_priority,
                             int intra_priority = 0) {
    request->ChangePriority(new_priority, intra_priority);
  }

  void FireCoalescingTimer() {
    EXPECT_TRUE(mock_timer_->IsRunning());
    mock_timer_->Fire();
  }

  ResourceScheduler* scheduler() {
    return scheduler_.get();
  }

  TestBrowserThreadBundle thread_bundle_;
  std::unique_ptr<ResourceScheduler> scheduler_;
  base::MockTimer* mock_timer_;
  net::HttpServerPropertiesImpl http_server_properties_;
  net::TestURLRequestContext context_;
};

TEST_F(ResourceSchedulerTest, OneIsolatedLowRequest) {
  std::unique_ptr<TestRequest> request(
      NewRequest("http://host/1", net::LOWEST));
  EXPECT_TRUE(request->started());
}

TEST_F(ResourceSchedulerTest, OneLowLoadsUntilBodyInserted) {
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));
  std::unique_ptr<TestRequest> low2(NewRequest("http://host/low", net::LOWEST));
  EXPECT_TRUE(high->started());
  EXPECT_TRUE(low->started());
  EXPECT_FALSE(low2->started());

  high.reset();
  base::RunLoop().RunUntilIdle();
  EXPECT_FALSE(low2->started());

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(low2->started());
}

TEST_F(ResourceSchedulerTest, OneLowLoadsUntilCriticalComplete) {
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));
  std::unique_ptr<TestRequest> low2(NewRequest("http://host/low", net::LOWEST));
  EXPECT_TRUE(high->started());
  EXPECT_TRUE(low->started());
  EXPECT_FALSE(low2->started());

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  base::RunLoop().RunUntilIdle();
  EXPECT_FALSE(low2->started());

  high.reset();
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(low2->started());
}

TEST_F(ResourceSchedulerTest, MediumDoesNotBlockCriticalComplete) {
  // kLayoutBlockingPriorityThreshold determines what priority level above which
  // requests are considered layout-blocking and must be completed before the
  // critical loading period is complete.  It is currently set to net::MEDIUM.
  std::unique_ptr<TestRequest> medium(
      NewRequest("http://host/low", net::MEDIUM));
  std::unique_ptr<TestRequest> lowest(
      NewRequest("http://host/lowest", net::LOWEST));
  std::unique_ptr<TestRequest> lowest2(
      NewRequest("http://host/lowest", net::LOWEST));
  EXPECT_TRUE(medium->started());
  EXPECT_TRUE(lowest->started());
  EXPECT_FALSE(lowest2->started());

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(lowest2->started());
}

TEST_F(ResourceSchedulerTest, SchedulerYieldsWithFeatureEnabled) {
  base::test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitFromCommandLine(kNetworkSchedulerYielding, "");
  InitializeScheduler();

  // Use spdy so that we don't throttle.
  http_server_properties_.SetSupportsSpdy(
      url::SchemeHostPort("https", "spdyhost", 443), true);

  // Add enough async requests that the last one should yield.
  std::vector<std::unique_ptr<TestRequest>> requests;
  for (int i = 0; i < kMaxRequestsBeforeYielding + 1; ++i)
    requests.push_back(NewRequest("http://host/higher", net::HIGHEST));

  // Verify that the number of requests before yielding started.
  for (int i = 0; i < kMaxRequestsBeforeYielding; ++i)
    EXPECT_TRUE(requests[i]->started());

  // The next async request should have yielded.
  EXPECT_FALSE(requests[kMaxRequestsBeforeYielding]->started());

  // Verify that with time the yielded request eventually runs.
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(requests[kMaxRequestsBeforeYielding]->started());
}

TEST_F(ResourceSchedulerTest, SchedulerDoesNotYieldForSyncRequests) {
  base::test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitFromCommandLine(kNetworkSchedulerYielding, "");
  InitializeScheduler();

  // Use spdy so that we don't throttle.
  http_server_properties_.SetSupportsSpdy(
      url::SchemeHostPort("https", "spdyhost", 443), true);

  // Add enough async requests that the last one should yield.
  std::vector<std::unique_ptr<TestRequest>> requests;
  for (int i = 0; i < kMaxRequestsBeforeYielding + 1; ++i)
    requests.push_back(NewRequest("http://host/higher", net::HIGHEST));

  // Add a sync requests.
  requests.push_back(NewSyncRequest("http://host/higher", net::HIGHEST));

  // Verify that the number of requests before yielding started.
  for (int i = 0; i < kMaxRequestsBeforeYielding; ++i)
    EXPECT_TRUE(requests[i]->started());

  // The next async request should have yielded.
  EXPECT_FALSE(requests[kMaxRequestsBeforeYielding]->started());

  // The next sync request should have started even though async is yielding.
  EXPECT_TRUE(requests[kMaxRequestsBeforeYielding + 1]->started());

  // Verify that with time the yielded request eventually runs.
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(requests[kMaxRequestsBeforeYielding]->started());
}

TEST_F(ResourceSchedulerTest, SchedulerDoesNotYieldForAlternativeSchemes) {
  base::test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitFromCommandLine(kNetworkSchedulerYielding, "");
  InitializeScheduler();

  // Use spdy so that we don't throttle.
  http_server_properties_.SetSupportsSpdy(
      url::SchemeHostPort("https", "spdyhost", 443), true);

  // Add enough async requests that the last one should yield.
  std::vector<std::unique_ptr<TestRequest>> requests;
  for (int i = 0; i < kMaxRequestsBeforeYielding + 1; ++i)
    requests.push_back(NewRequest("http://host/higher", net::HIGHEST));

  // Add a non-http request.
  requests.push_back(NewRequest("zzz://host/higher", net::HIGHEST));

  // Verify that the number of requests before yielding started.
  for (int i = 0; i < kMaxRequestsBeforeYielding; ++i)
    EXPECT_TRUE(requests[i]->started());

  // The next async request should have yielded.
  EXPECT_FALSE(requests[kMaxRequestsBeforeYielding]->started());

  // The non-http(s) request should have started even though async is
  // yielding.
  EXPECT_TRUE(requests[kMaxRequestsBeforeYielding + 1]->started());

  // Verify that with time the yielded request eventually runs.
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(requests[kMaxRequestsBeforeYielding]->started());
}

TEST_F(ResourceSchedulerTest, SchedulerDoesNotYieldWithFeatureDisabled) {
  base::test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitFromCommandLine("", kNetworkSchedulerYielding);
  InitializeScheduler();

  // Use spdy so that we don't throttle.
  http_server_properties_.SetSupportsSpdy(
      url::SchemeHostPort("https", "spdyhost", 443), true);

  // Add enough async requests that the last one would yield if yielding were
  // enabled.
  std::vector<std::unique_ptr<TestRequest>> requests;
  for (int i = 0; i < kMaxRequestsBeforeYielding + 1; ++i)
    requests.push_back(NewRequest("http://host/higher", net::HIGHEST));

  // Verify that none of the requests yield.
  for (int i = 0; i < kMaxRequestsBeforeYielding + 1; ++i)
    EXPECT_TRUE(requests[i]->started());
}

TEST_F(ResourceSchedulerTest, OneLowLoadsUntilBodyInsertedExceptSpdy) {
  base::test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitFromCommandLine("",
                                          kPrioritySupportedRequestsDelayable);
  InitializeScheduler();

  http_server_properties_.SetSupportsSpdy(
      url::SchemeHostPort("https", "spdyhost", 443), true);
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));
  std::unique_ptr<TestRequest> low2(NewRequest("http://host/low", net::LOWEST));
  std::unique_ptr<TestRequest> low_spdy(
      NewRequest("https://spdyhost/low", net::LOWEST));
  EXPECT_TRUE(high->started());
  EXPECT_TRUE(low->started());
  EXPECT_FALSE(low2->started());
  EXPECT_TRUE(low_spdy->started());

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  high.reset();
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(low2->started());
}

TEST_F(ResourceSchedulerTest,
       OneLowLoadsUntilBodyInsertedEvenSpdyWhenDelayable) {
  base::test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitFromCommandLine(kPrioritySupportedRequestsDelayable,
                                          "");

  InitializeScheduler();
  http_server_properties_.SetSupportsSpdy(
      url::SchemeHostPort("https", "spdyhost", 443), true);
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));
  std::unique_ptr<TestRequest> low2(NewRequest("http://host/low", net::LOWEST));
  std::unique_ptr<TestRequest> low_spdy(
      NewRequest("https://spdyhost/low", net::LOWEST));
  EXPECT_TRUE(high->started());
  EXPECT_TRUE(low->started());
  EXPECT_FALSE(low2->started());
  EXPECT_FALSE(low_spdy->started());

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  high.reset();
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(low2->started());
}

TEST_F(ResourceSchedulerTest, SpdyLowBlocksOtherLowUntilBodyInserted) {
  http_server_properties_.SetSupportsSpdy(
      url::SchemeHostPort("https", "spdyhost", 443), true);
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low_spdy(
      NewRequest("https://spdyhost/low", net::LOWEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));
  EXPECT_TRUE(high->started());
  EXPECT_TRUE(low_spdy->started());
  EXPECT_FALSE(low->started());

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  high.reset();
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(low->started());
}

TEST_F(ResourceSchedulerTest, NavigationResetsState) {
  base::HistogramTester histogram_tester;
  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  scheduler()->OnNavigate(kChildId, kRouteId);

  {
    std::unique_ptr<TestRequest> high(
        NewRequest("http://host/high", net::HIGHEST));
    std::unique_ptr<TestRequest> low(
        NewRequest("http://host/low", net::LOWEST));
    std::unique_ptr<TestRequest> low2(
        NewRequest("http://host/low", net::LOWEST));
    EXPECT_TRUE(high->started());
    EXPECT_TRUE(low->started());
    EXPECT_FALSE(low2->started());
  }

  histogram_tester.ExpectTotalCount("ResourceScheduler.RequestsCount.All", 2);
  EXPECT_THAT(
      histogram_tester.GetAllSamples("ResourceScheduler.RequestsCount.All"),
      testing::ElementsAre(base::Bucket(1, 1), base::Bucket(2, 1)));

  histogram_tester.ExpectTotalCount("ResourceScheduler.RequestsCount.Delayable",
                                    2);
  histogram_tester.ExpectTotalCount(
      "ResourceScheduler.RequestsCount.NonDelayable", 2);
  histogram_tester.ExpectTotalCount(
      "ResourceScheduler.RequestsCount.TotalLayoutBlocking", 2);

  histogram_tester.ExpectUniqueSample(
      "ResourceScheduler.PeakDelayableRequestsInFlight.LayoutBlocking", 1, 1);
  histogram_tester.ExpectUniqueSample(
      "ResourceScheduler.PeakDelayableRequestsInFlight.NonDelayable", 1, 1);
}

TEST_F(ResourceSchedulerTest, BackgroundRequestStartsImmediately) {
  const int route_id = 0;  // Indicates a background request.
  std::unique_ptr<TestRequest> request(
      NewRequestWithRoute("http://host/1", net::LOWEST, route_id));
  EXPECT_TRUE(request->started());
}

TEST_F(ResourceSchedulerTest, MoreThanOneHighRequestBlocksDelayableRequests) {
  // If there are more than kInFlightNonDelayableRequestCountThreshold (=1)
  // high-priority / non-delayable requests, block all low priority fetches and
  // allow them through one at a time once the number of high priority requests
  // drops.
  std::unique_ptr<TestRequest> high1(
      NewRequest("http://host/high1", net::HIGHEST));
  std::unique_ptr<TestRequest> high2(
      NewRequest("http://host/high2", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));
  std::unique_ptr<TestRequest> low2(NewRequest("http://host/low", net::LOWEST));
  EXPECT_TRUE(high1->started());
  EXPECT_TRUE(high2->started());
  EXPECT_FALSE(low->started());
  EXPECT_FALSE(low2->started());

  high1.reset();
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(low->started());
  EXPECT_FALSE(low2->started());
}

TEST_F(ResourceSchedulerTest, CancelOtherRequestsWhileResuming) {
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low1(
      NewRequest("http://host/low1", net::LOWEST));

  std::unique_ptr<net::URLRequest> url_request(
      NewURLRequest("http://host/low2", net::LOWEST));
  std::unique_ptr<ResourceThrottle> throttle(scheduler()->ScheduleRequest(
      kChildId, kRouteId, true, url_request.get()));
  std::unique_ptr<CancelingTestRequest> low2(new CancelingTestRequest(
      std::move(url_request), std::move(throttle), scheduler()));
  low2->Start();

  std::unique_ptr<TestRequest> low3(
      NewRequest("http://host/low3", net::LOWEST));
  low2->set_request_to_cancel(std::move(low3));
  std::unique_ptr<TestRequest> low4(
      NewRequest("http://host/low4", net::LOWEST));

  EXPECT_TRUE(high->started());
  EXPECT_FALSE(low2->started());

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  high.reset();
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(low1->started());
  EXPECT_TRUE(low2->started());
  EXPECT_TRUE(low4->started());
}

TEST_F(ResourceSchedulerTest, LimitedNumberOfDelayableRequestsInFlight) {
  // The yielding feature will sometimes yield requests before they get a
  // chance to start, which conflicts this test. So disable the feature.
  base::test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitFromCommandLine("", kNetworkSchedulerYielding);

  // We only load low priority resources if there's a body.
  scheduler()->OnWillInsertBody(kChildId, kRouteId);

  // Throw in one high priority request to make sure that's not a factor.
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  EXPECT_TRUE(high->started());

  const int kMaxNumDelayableRequestsPerClient = 10;  // Should match the .cc.
  const int kMaxNumDelayableRequestsPerHost = 6;
  std::vector<std::unique_ptr<TestRequest>> lows_singlehost;
  // Queue up to the per-host limit (we subtract the current high-pri request).
  for (int i = 0; i < kMaxNumDelayableRequestsPerHost - 1; ++i) {
    string url = "http://host/low" + base::IntToString(i);
    lows_singlehost.push_back(NewRequest(url.c_str(), net::LOWEST));
    EXPECT_TRUE(lows_singlehost[i]->started());
  }

  std::unique_ptr<TestRequest> second_last_singlehost(
      NewRequest("http://host/last", net::LOWEST));
  std::unique_ptr<TestRequest> last_singlehost(
      NewRequest("http://host/s_last", net::LOWEST));

  EXPECT_FALSE(second_last_singlehost->started());

  high.reset();
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(second_last_singlehost->started());
  EXPECT_FALSE(last_singlehost->started());

  lows_singlehost.erase(lows_singlehost.begin());
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(last_singlehost->started());

  // Queue more requests from different hosts until we reach the total limit.
  int expected_slots_left =
      kMaxNumDelayableRequestsPerClient - kMaxNumDelayableRequestsPerHost;
  EXPECT_GT(expected_slots_left, 0);
  std::vector<std::unique_ptr<TestRequest>> lows_different_host;
  base::RunLoop().RunUntilIdle();
  for (int i = 0; i < expected_slots_left; ++i) {
    string url = "http://host" + base::IntToString(i) + "/low";
    lows_different_host.push_back(NewRequest(url.c_str(), net::LOWEST));
    EXPECT_TRUE(lows_different_host[i]->started());
  }

  std::unique_ptr<TestRequest> last_different_host(
      NewRequest("http://host_new/last", net::LOWEST));
  EXPECT_FALSE(last_different_host->started());
}

TEST_F(ResourceSchedulerTest, RaisePriorityAndStart) {
  // Dummies to enforce scheduling.
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/req", net::LOWEST));

  std::unique_ptr<TestRequest> request(
      NewRequest("http://host/req", net::LOWEST));
  EXPECT_FALSE(request->started());

  ChangeRequestPriority(request.get(), net::HIGHEST);
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(request->started());
}

TEST_F(ResourceSchedulerTest, RaisePriorityInQueue) {
  // Dummies to enforce scheduling.
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));

  std::unique_ptr<TestRequest> request(
      NewRequest("http://host/req", net::IDLE));
  std::unique_ptr<TestRequest> idle(NewRequest("http://host/idle", net::IDLE));
  EXPECT_FALSE(request->started());
  EXPECT_FALSE(idle->started());

  ChangeRequestPriority(request.get(), net::LOWEST);
  base::RunLoop().RunUntilIdle();
  EXPECT_FALSE(request->started());
  EXPECT_FALSE(idle->started());

  const int kMaxNumDelayableRequestsPerClient = 10;  // Should match the .cc.
  std::vector<std::unique_ptr<TestRequest>> lows;
  for (int i = 0; i < kMaxNumDelayableRequestsPerClient - 1; ++i) {
    string url = "http://host/low" + base::IntToString(i);
    lows.push_back(NewRequest(url.c_str(), net::LOWEST));
  }

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  high.reset();
  base::RunLoop().RunUntilIdle();

  EXPECT_TRUE(request->started());
  EXPECT_FALSE(idle->started());
}

TEST_F(ResourceSchedulerTest, LowerPriority) {
  // Dummies to enforce scheduling.
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));

  std::unique_ptr<TestRequest> request(
      NewRequest("http://host/req", net::LOWEST));
  std::unique_ptr<TestRequest> idle(NewRequest("http://host/idle", net::IDLE));
  EXPECT_FALSE(request->started());
  EXPECT_FALSE(idle->started());

  ChangeRequestPriority(request.get(), net::IDLE);
  base::RunLoop().RunUntilIdle();
  EXPECT_FALSE(request->started());
  EXPECT_FALSE(idle->started());

  const int kMaxNumDelayableRequestsPerClient = 10;  // Should match the .cc.
  // 2 fewer filler requests: 1 for the "low" dummy at the start, and 1 for the
  // one at the end, which will be tested.
  const int kNumFillerRequests = kMaxNumDelayableRequestsPerClient - 2;
  std::vector<std::unique_ptr<TestRequest>> lows;
  for (int i = 0; i < kNumFillerRequests; ++i) {
    string url = "http://host" + base::IntToString(i) + "/low";
    lows.push_back(NewRequest(url.c_str(), net::LOWEST));
  }

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  high.reset();
  base::RunLoop().RunUntilIdle();

  EXPECT_FALSE(request->started());
  EXPECT_TRUE(idle->started());
}

TEST_F(ResourceSchedulerTest, ReprioritizedRequestGoesToBackOfQueue) {
  // Dummies to enforce scheduling.
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));

  std::unique_ptr<TestRequest> request(
      NewRequest("http://host/req", net::LOWEST));
  std::unique_ptr<TestRequest> idle(NewRequest("http://host/idle", net::IDLE));
  EXPECT_FALSE(request->started());
  EXPECT_FALSE(idle->started());

  const int kMaxNumDelayableRequestsPerClient = 10;  // Should match the .cc.
  std::vector<std::unique_ptr<TestRequest>> lows;
  for (int i = 0; i < kMaxNumDelayableRequestsPerClient; ++i) {
    string url = "http://host/low" + base::IntToString(i);
    lows.push_back(NewRequest(url.c_str(), net::LOWEST));
  }

  ChangeRequestPriority(request.get(), net::IDLE);
  base::RunLoop().RunUntilIdle();
  EXPECT_FALSE(request->started());
  EXPECT_FALSE(idle->started());

  ChangeRequestPriority(request.get(), net::LOWEST);
  base::RunLoop().RunUntilIdle();
  EXPECT_FALSE(request->started());
  EXPECT_FALSE(idle->started());

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  base::RunLoop().RunUntilIdle();
  EXPECT_FALSE(request->started());
  EXPECT_FALSE(idle->started());
}

TEST_F(ResourceSchedulerTest, HigherIntraPriorityGoesToFrontOfQueue) {
  // Dummies to enforce scheduling.
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));

  const int kMaxNumDelayableRequestsPerClient = 10;  // Should match the .cc.
  std::vector<std::unique_ptr<TestRequest>> lows;
  for (int i = 0; i < kMaxNumDelayableRequestsPerClient; ++i) {
    string url = "http://host/low" + base::IntToString(i);
    lows.push_back(NewRequest(url.c_str(), net::IDLE));
  }

  std::unique_ptr<TestRequest> request(
      NewRequest("http://host/req", net::IDLE));
  EXPECT_FALSE(request->started());

  ChangeRequestPriority(request.get(), net::IDLE, 1);
  base::RunLoop().RunUntilIdle();
  EXPECT_FALSE(request->started());

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  high.reset();
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(request->started());
}

TEST_F(ResourceSchedulerTest, NonHTTPSchedulesImmediately) {
  // Dummies to enforce scheduling.
  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));

  std::unique_ptr<TestRequest> request(
      NewRequest("chrome-extension://req", net::LOWEST));
  EXPECT_TRUE(request->started());
}

TEST_F(ResourceSchedulerTest, SpdyProxySchedulesImmediately) {
  base::test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitFromCommandLine("",
                                          kPrioritySupportedRequestsDelayable);
  InitializeScheduler();

  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));

  std::unique_ptr<TestRequest> request(
      NewRequest("http://host/req", net::IDLE));
  EXPECT_FALSE(request->started());

  scheduler()->OnReceivedSpdyProxiedHttpResponse(kChildId, kRouteId);
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(request->started());

  std::unique_ptr<TestRequest> after(
      NewRequest("http://host/after", net::IDLE));
  EXPECT_TRUE(after->started());
}

TEST_F(ResourceSchedulerTest, SpdyProxyDelayable) {
  base::test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitFromCommandLine(kPrioritySupportedRequestsDelayable,
                                          "");
  InitializeScheduler();

  std::unique_ptr<TestRequest> high(
      NewRequest("http://host/high", net::HIGHEST));
  std::unique_ptr<TestRequest> low(NewRequest("http://host/low", net::LOWEST));

  std::unique_ptr<TestRequest> request(
      NewRequest("http://host/req", net::IDLE));
  EXPECT_FALSE(request->started());

  scheduler()->OnReceivedSpdyProxiedHttpResponse(kChildId, kRouteId);
  base::RunLoop().RunUntilIdle();
  EXPECT_FALSE(request->started());

  std::unique_ptr<TestRequest> after(
      NewRequest("http://host/after", net::IDLE));
  EXPECT_FALSE(after->started());
}

TEST_F(ResourceSchedulerTest, NewSpdyHostInDelayableRequests) {
  base::test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitFromCommandLine("",
                                          kPrioritySupportedRequestsDelayable);
  InitializeScheduler();

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  const int kMaxNumDelayableRequestsPerClient = 10;  // Should match the .cc.

  std::unique_ptr<TestRequest> low1_spdy(
      NewRequest("http://spdyhost1:8080/low", net::LOWEST));
  // Cancel a request after we learn the server supports SPDY.
  std::vector<std::unique_ptr<TestRequest>> lows;
  for (int i = 0; i < kMaxNumDelayableRequestsPerClient - 1; ++i) {
    string url = "http://host" + base::IntToString(i) + "/low";
    lows.push_back(NewRequest(url.c_str(), net::LOWEST));
  }
  std::unique_ptr<TestRequest> low1(NewRequest("http://host/low", net::LOWEST));
  EXPECT_FALSE(low1->started());
  http_server_properties_.SetSupportsSpdy(
      url::SchemeHostPort("http", "spdyhost1", 8080), true);
  low1_spdy.reset();
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(low1->started());

  low1.reset();
  base::RunLoop().RunUntilIdle();
  std::unique_ptr<TestRequest> low2_spdy(
      NewRequest("http://spdyhost2:8080/low", net::IDLE));
  // Reprioritize a request after we learn the server supports SPDY.
  EXPECT_TRUE(low2_spdy->started());
  http_server_properties_.SetSupportsSpdy(
      url::SchemeHostPort("http", "spdyhost2", 8080), true);
  ChangeRequestPriority(low2_spdy.get(), net::LOWEST);
  base::RunLoop().RunUntilIdle();
  std::unique_ptr<TestRequest> low2(NewRequest("http://host/low", net::LOWEST));
  EXPECT_TRUE(low2->started());
}

TEST_F(ResourceSchedulerTest, NewDelayableSpdyHostInDelayableRequests) {
  base::test::ScopedFeatureList scoped_feature_list;
  scoped_feature_list.InitFromCommandLine(kPrioritySupportedRequestsDelayable,
                                          "");
  InitializeScheduler();

  scheduler()->OnWillInsertBody(kChildId, kRouteId);
  const int kMaxNumDelayableRequestsPerClient = 10;  // Should match the .cc.

  std::unique_ptr<TestRequest> low1_spdy(
      NewRequest("http://spdyhost1:8080/low", net::LOWEST));
  // Cancel a request after we learn the server supports SPDY.
  std::vector<std::unique_ptr<TestRequest>> lows;
  for (int i = 0; i < kMaxNumDelayableRequestsPerClient - 1; ++i) {
    string url = "http://host" + base::IntToString(i) + "/low";
    lows.push_back(NewRequest(url.c_str(), net::LOWEST));
  }
  std::unique_ptr<TestRequest> low1(NewRequest("http://host/low", net::LOWEST));
  EXPECT_FALSE(low1->started());
  http_server_properties_.SetSupportsSpdy(
      url::SchemeHostPort("http", "spdyhost1", 8080), true);
  low1_spdy.reset();
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(low1->started());

  low1.reset();
  base::RunLoop().RunUntilIdle();
  std::unique_ptr<TestRequest> low2_spdy(
      NewRequest("http://spdyhost2:8080/low", net::IDLE));
  // Reprioritize a request after we learn the server supports SPDY.
  EXPECT_TRUE(low2_spdy->started());
  http_server_properties_.SetSupportsSpdy(
      url::SchemeHostPort("http", "spdyhost2", 8080), true);
  ChangeRequestPriority(low2_spdy.get(), net::LOWEST);
  base::RunLoop().RunUntilIdle();
  std::unique_ptr<TestRequest> low2(NewRequest("http://host/low", net::LOWEST));
  EXPECT_FALSE(low2->started());
}

// Async revalidations which are not started when the tab is closed must be
// started at some point, or they will hang around forever and prevent other
// async revalidations to the same URL from being issued.
TEST_F(ResourceSchedulerTest, RequestStartedAfterClientDeleted) {
  scheduler_->OnClientCreated(kChildId2, kRouteId2);
  std::unique_ptr<TestRequest> high(NewRequestWithChildAndRoute(
      "http://host/high", net::HIGHEST, kChildId2, kRouteId2));
  std::unique_ptr<TestRequest> lowest1(NewRequestWithChildAndRoute(
      "http://host/lowest", net::LOWEST, kChildId2, kRouteId2));
  std::unique_ptr<TestRequest> lowest2(NewRequestWithChildAndRoute(
      "http://host/lowest", net::LOWEST, kChildId2, kRouteId2));
  EXPECT_FALSE(lowest2->started());

  scheduler_->OnClientDeleted(kChildId2, kRouteId2);
  high.reset();
  lowest1.reset();
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(lowest2->started());
}

// The ResourceScheduler::Client destructor calls
// LoadAnyStartablePendingRequests(), which may start some pending requests.
// This test is to verify that requests will be started at some point
// even if they were not started by the destructor.
TEST_F(ResourceSchedulerTest, RequestStartedAfterClientDeletedManyDelayable) {
  scheduler_->OnClientCreated(kChildId2, kRouteId2);
  std::unique_ptr<TestRequest> high(NewRequestWithChildAndRoute(
      "http://host/high", net::HIGHEST, kChildId2, kRouteId2));
  const int kMaxNumDelayableRequestsPerClient = 10;
  std::vector<std::unique_ptr<TestRequest>> delayable_requests;
  for (int i = 0; i < kMaxNumDelayableRequestsPerClient + 1; ++i) {
    delayable_requests.push_back(NewRequestWithChildAndRoute(
        "http://host/lowest", net::LOWEST, kChildId2, kRouteId2));
  }
  std::unique_ptr<TestRequest> lowest(NewRequestWithChildAndRoute(
      "http://host/lowest", net::LOWEST, kChildId2, kRouteId2));
  EXPECT_FALSE(lowest->started());

  scheduler_->OnClientDeleted(kChildId2, kRouteId2);
  high.reset();
  delayable_requests.clear();
  base::RunLoop().RunUntilIdle();
  EXPECT_TRUE(lowest->started());
}

}  // unnamed namespace

}  // namespace content