diff --git a/android_webview/browser/aw_content_browser_client.cc b/android_webview/browser/aw_content_browser_client.cc
index a63cb61..ebc4a7d 100644
--- a/android_webview/browser/aw_content_browser_client.cc
+++ b/android_webview/browser/aw_content_browser_client.cc
@@ -481,15 +481,6 @@
   return rb.GetImageNamed(IDR_DEFAULT_FAVICON).AsImageSkia();
 }
 
-bool AwContentBrowserClient::AllowAppCacheOnIO(
-    const GURL& manifest_url,
-    const GURL& first_party,
-    content::ResourceContext* context) {
-  // WebView doesn't have a per-site policy for locally stored data,
-  // instead AppCache can be disabled for individual WebViews.
-  return true;
-}
-
 bool AwContentBrowserClient::AllowAppCache(const GURL& manifest_url,
                                            const GURL& first_party,
                                            content::BrowserContext* context) {
@@ -785,47 +776,6 @@
 }
 
 std::vector<std::unique_ptr<blink::URLLoaderThrottle>>
-AwContentBrowserClient::CreateURLLoaderThrottlesOnIO(
-    const network::ResourceRequest& request,
-    content::ResourceContext* resource_context,
-    const base::RepeatingCallback<content::WebContents*()>& wc_getter,
-    content::NavigationUIData* navigation_ui_data,
-    int frame_tree_node_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  DCHECK(!base::FeatureList::IsEnabled(::features::kNavigationLoaderOnUI));
-
-  std::vector<std::unique_ptr<blink::URLLoaderThrottle>> result;
-
-  if (base::FeatureList::IsEnabled(network::features::kNetworkService) ||
-      base::FeatureList::IsEnabled(safe_browsing::kCheckByURLLoaderThrottle)) {
-    result.push_back(safe_browsing::BrowserURLLoaderThrottle::Create(
-        base::BindOnce(
-            [](AwContentBrowserClient* client, content::ResourceContext*) {
-              return client->GetSafeBrowsingUrlCheckerDelegate();
-            },
-            base::Unretained(this)),
-        wc_getter, frame_tree_node_id, resource_context));
-  }
-
-  if (request.resource_type ==
-      static_cast<int>(content::ResourceType::kMainFrame)) {
-    const bool is_load_url =
-        request.transition_type & ui::PAGE_TRANSITION_FROM_API;
-    const bool is_go_back_forward =
-        request.transition_type & ui::PAGE_TRANSITION_FORWARD_BACK;
-    const bool is_reload = ui::PageTransitionCoreTypeIs(
-        static_cast<ui::PageTransition>(request.transition_type),
-        ui::PAGE_TRANSITION_RELOAD);
-    if (is_load_url || is_go_back_forward || is_reload) {
-      result.push_back(std::make_unique<AwURLLoaderThrottle>(
-          static_cast<AwResourceContext*>(resource_context)));
-    }
-  }
-
-  return result;
-}
-
-std::vector<std::unique_ptr<blink::URLLoaderThrottle>>
 AwContentBrowserClient::CreateURLLoaderThrottles(
     const network::ResourceRequest& request,
     content::BrowserContext* browser_context,
diff --git a/android_webview/browser/aw_content_browser_client.h b/android_webview/browser/aw_content_browser_client.h
index 744a9a9..485f5d4 100644
--- a/android_webview/browser/aw_content_browser_client.h
+++ b/android_webview/browser/aw_content_browser_client.h
@@ -75,9 +75,6 @@
   std::string GetApplicationLocale() override;
   std::string GetAcceptLangs(content::BrowserContext* context) override;
   gfx::ImageSkia GetDefaultFavicon() override;
-  bool AllowAppCacheOnIO(const GURL& manifest_url,
-                         const GURL& first_party,
-                         content::ResourceContext* context) override;
   bool AllowAppCache(const GURL& manifest_url,
                      const GURL& first_party,
                      content::BrowserContext* context) override;
@@ -168,13 +165,6 @@
       service_manager::BinderRegistry* registry,
       content::RenderFrameHost* render_frame_host) override;
   std::vector<std::unique_ptr<blink::URLLoaderThrottle>>
-  CreateURLLoaderThrottlesOnIO(
-      const network::ResourceRequest& request,
-      content::ResourceContext* resource_context,
-      const base::RepeatingCallback<content::WebContents*()>& wc_getter,
-      content::NavigationUIData* navigation_ui_data,
-      int frame_tree_node_id) override;
-  std::vector<std::unique_ptr<blink::URLLoaderThrottle>>
   CreateURLLoaderThrottles(
       const network::ResourceRequest& request,
       content::BrowserContext* browser_context,
diff --git a/chrome/browser/browsing_data/browsing_data_appcache_helper.cc b/chrome/browser/browsing_data/browsing_data_appcache_helper.cc
index c36a096..189a46a 100644
--- a/chrome/browser/browsing_data/browsing_data_appcache_helper.cc
+++ b/chrome/browser/browsing_data/browsing_data_appcache_helper.cc
@@ -18,7 +18,6 @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/storage_partition.h"
 #include "content/public/browser/storage_usage_info.h"
-#include "content/public/common/content_features.h"
 #include "net/base/completion_once_callback.h"
 #include "third_party/blink/public/mojom/appcache/appcache_info.mojom.h"
 
@@ -57,12 +56,7 @@
     result.emplace_back(origin, total_size, last_modified);
   }
 
-  if (base::FeatureList::IsEnabled(features::kNavigationLoaderOnUI)) {
-    std::move(callback).Run(std::move(result));
-  } else {
-    base::PostTask(FROM_HERE, {BrowserThread::UI},
-                   base::BindOnce(std::move(callback), std::move(result)));
-  }
+  std::move(callback).Run(std::move(result));
 }
 
 }  // namespace
@@ -75,35 +69,6 @@
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
   DCHECK(!callback.is_null());
 
-  if (base::FeatureList::IsEnabled(features::kNavigationLoaderOnUI)) {
-    StartFetchingOnLoaderThread(std::move(callback));
-  } else {
-    base::PostTask(
-        FROM_HERE, {BrowserThread::IO},
-        base::BindOnce(&BrowsingDataAppCacheHelper::StartFetchingOnLoaderThread,
-                       this, std::move(callback)));
-  }
-}
-
-void BrowsingDataAppCacheHelper::DeleteAppCaches(const url::Origin& origin) {
-  DCHECK_CURRENTLY_ON(BrowserThread::UI);
-  if (base::FeatureList::IsEnabled(features::kNavigationLoaderOnUI)) {
-    DeleteAppCachesOnLoaderThread(origin);
-  } else {
-    base::PostTask(
-        FROM_HERE, {BrowserThread::IO},
-        base::BindOnce(
-            &BrowsingDataAppCacheHelper::DeleteAppCachesOnLoaderThread, this,
-            origin));
-  }
-}
-
-BrowsingDataAppCacheHelper::~BrowsingDataAppCacheHelper() {}
-
-void BrowsingDataAppCacheHelper::StartFetchingOnLoaderThread(
-    FetchCallback callback) {
-  DCHECK(!callback.is_null());
-
   scoped_refptr<content::AppCacheInfoCollection> info_collection =
       new content::AppCacheInfoCollection();
 
@@ -113,12 +78,14 @@
                      info_collection));
 }
 
-void BrowsingDataAppCacheHelper::DeleteAppCachesOnLoaderThread(
-    const url::Origin& origin) {
+void BrowsingDataAppCacheHelper::DeleteAppCaches(const url::Origin& origin) {
+  DCHECK_CURRENTLY_ON(BrowserThread::UI);
   appcache_service_->DeleteAppCachesForOrigin(origin,
                                               net::CompletionOnceCallback());
 }
 
+BrowsingDataAppCacheHelper::~BrowsingDataAppCacheHelper() {}
+
 CannedBrowsingDataAppCacheHelper::CannedBrowsingDataAppCacheHelper(
     AppCacheService* appcache_service)
     : BrowsingDataAppCacheHelper(appcache_service) {}
diff --git a/chrome/browser/browsing_data/browsing_data_appcache_helper.h b/chrome/browser/browsing_data/browsing_data_appcache_helper.h
index ae536da..557f2648 100644
--- a/chrome/browser/browsing_data/browsing_data_appcache_helper.h
+++ b/chrome/browser/browsing_data/browsing_data_appcache_helper.h
@@ -41,9 +41,6 @@
   virtual ~BrowsingDataAppCacheHelper();
 
  private:
-  void StartFetchingOnLoaderThread(FetchCallback completion_callback);
-  void DeleteAppCachesOnLoaderThread(const url::Origin& origin);
-
   // Owned by the profile.
   content::AppCacheService* appcache_service_;
 
diff --git a/chrome/browser/captive_portal/captive_portal_browsertest.cc b/chrome/browser/captive_portal/captive_portal_browsertest.cc
index 61547350..86715b2 100644
--- a/chrome/browser/captive_portal/captive_portal_browsertest.cc
+++ b/chrome/browser/captive_portal/captive_portal_browsertest.cc
@@ -16,7 +16,6 @@
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/compiler_specific.h"
-#include "base/feature_list.h"
 #include "base/files/file_path.h"
 #include "base/macros.h"
 #include "base/message_loop/message_loop.h"
@@ -67,7 +66,6 @@
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/storage_partition.h"
 #include "content/public/browser/web_contents.h"
-#include "content/public/common/content_features.h"
 #include "content/public/common/url_constants.h"
 #include "content/public/test/browser_test_utils.h"
 #include "content/public/test/url_loader_interceptor.h"
@@ -83,7 +81,6 @@
 #include "net/url_request/url_request_context.h"
 #include "net/url_request/url_request_context_getter.h"
 #include "net/url_request/url_request_status.h"
-#include "services/network/public/cpp/features.h"
 #include "testing/gtest/include/gtest/gtest.h"
 
 using captive_portal::CaptivePortalResult;
@@ -158,12 +155,6 @@
 // captive portal.
 const char* const kInternetConnectedTitle = "Title Of Awesomeness";
 
-BrowserThread::ID GetInterceptorThreadID() {
-  return base::FeatureList::IsEnabled(features::kNavigationLoaderOnUI)
-             ? BrowserThread::UI
-             : BrowserThread::IO;
-}
-
 // Creates a server-side redirect for use with the TestServer.
 std::string CreateServerRedirect(const std::string& dest_url) {
   const char* const kServerRedirectBase = "/server-redirect?";
@@ -762,11 +753,11 @@
 
   // Waits for exactly |num_jobs| kMockHttps* requests.
   void WaitForJobs(int num_jobs) {
-    if (BrowserThread::CurrentlyOn(GetInterceptorThreadID())) {
+    if (BrowserThread::CurrentlyOn(BrowserThread::UI)) {
       SetNumJobsToWaitForOnInterceptorThread(num_jobs);
     } else {
       base::PostTaskWithTraits(
-          FROM_HERE, {GetInterceptorThreadID()},
+          FROM_HERE, {BrowserThread::UI},
           base::BindOnce(
               &CaptivePortalBrowserTest::SetNumJobsToWaitForOnInterceptorThread,
               base::Unretained(this), num_jobs));
@@ -779,7 +770,7 @@
   }
 
   void SetNumJobsToWaitForOnInterceptorThread(int num_jobs) {
-    DCHECK_CURRENTLY_ON(GetInterceptorThreadID());
+    DCHECK_CURRENTLY_ON(BrowserThread::UI);
     DCHECK(!num_jobs_to_wait_for_);
 
     int num_ongoing_jobs = static_cast<int>(ongoing_mock_requests_.size());
@@ -800,9 +791,9 @@
   // failure.  The only way to guarantee this is with an earlier call to
   // WaitForJobs, so makes sure there has been a matching WaitForJobs call.
   void FailJobs(int expected_num_jobs) {
-    if (!BrowserThread::CurrentlyOn(GetInterceptorThreadID())) {
+    if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
       base::PostTaskWithTraits(
-          FROM_HERE, {GetInterceptorThreadID()},
+          FROM_HERE, {BrowserThread::UI},
           base::BindOnce(&CaptivePortalBrowserTest::FailJobs,
                          base::Unretained(this), expected_num_jobs));
       return;
@@ -821,9 +812,9 @@
   // |expected_num_jobs| behaves just as in FailJobs.
   void FailJobsWithCertError(int expected_num_jobs,
                              const net::SSLInfo& ssl_info) {
-    if (!BrowserThread::CurrentlyOn(GetInterceptorThreadID())) {
+    if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
       base::PostTaskWithTraits(
-          FROM_HERE, {GetInterceptorThreadID()},
+          FROM_HERE, {BrowserThread::UI},
           base::BindOnce(&CaptivePortalBrowserTest::FailJobsWithCertError,
                          base::Unretained(this), expected_num_jobs, ssl_info));
       return;
@@ -863,9 +854,9 @@
   // Abandon all active kMockHttps* requests.  |expected_num_jobs|
   // behaves just as in FailJobs.
   void AbandonJobs(int expected_num_jobs) {
-    if (!BrowserThread::CurrentlyOn(GetInterceptorThreadID())) {
+    if (!BrowserThread::CurrentlyOn(BrowserThread::UI)) {
       base::PostTaskWithTraits(
-          FROM_HERE, {GetInterceptorThreadID()},
+          FROM_HERE, {BrowserThread::UI},
           base::BindOnce(&CaptivePortalBrowserTest::AbandonJobs,
                          base::Unretained(this), expected_num_jobs));
       return;
@@ -898,7 +889,7 @@
  protected:
   std::unique_ptr<content::URLLoaderInterceptor> url_loader_interceptor_;
   std::unique_ptr<base::RunLoop> run_loop_;
-  // Only accessed on the |GetInterceptorThreadID()| thread.
+  // Only accessed on the UI thread.
   int num_jobs_to_wait_for_ = 0;
   std::vector<content::URLLoaderInterceptor::RequestParams>
       ongoing_mock_requests_;
@@ -942,7 +933,7 @@
     content::URLLoaderInterceptor::RequestParams* params) {
   if (params->url_request.url.path() == kMockHttpsBadCertPath &&
       intercept_bad_cert_) {
-    CHECK(BrowserThread::CurrentlyOn(GetInterceptorThreadID()));
+    CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
     ongoing_mock_requests_.emplace_back(std::move(*params));
     return true;
   }
@@ -965,7 +956,7 @@
   if (url_string == kMockHttpsUrl || url_string == kMockHttpsUrl2 ||
       url_string == kMockHttpsQuickTimeoutUrl ||
       params->url_request.url.path() == kRedirectToMockHttpsPath) {
-    CHECK(BrowserThread::CurrentlyOn(GetInterceptorThreadID()));
+    CHECK(BrowserThread::CurrentlyOn(BrowserThread::UI));
     if (params->url_request.url.path() == kRedirectToMockHttpsPath) {
       net::RedirectInfo redirect_info;
       redirect_info.new_url = GURL(kMockHttpsUrl);
diff --git a/chrome/browser/chrome_content_browser_client.cc b/chrome/browser/chrome_content_browser_client.cc
index cd12cdb..bdf21f77 100644
--- a/chrome/browser/chrome_content_browser_client.cc
+++ b/chrome/browser/chrome_content_browser_client.cc
@@ -2349,17 +2349,6 @@
       out_prefs, Profile::FromBrowserContext(browser_context));
 }
 
-bool ChromeContentBrowserClient::AllowAppCacheOnIO(
-    const GURL& manifest_url,
-    const GURL& first_party,
-    content::ResourceContext* context) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  DCHECK(!base::FeatureList::IsEnabled(features::kNavigationLoaderOnUI));
-  ProfileIOData* io_data = ProfileIOData::FromResourceContext(context);
-  return io_data->GetCookieSettings()->IsCookieAccessAllowed(manifest_url,
-                                                             first_party);
-}
-
 bool ChromeContentBrowserClient::AllowAppCache(
     const GURL& manifest_url,
     const GURL& first_party,
@@ -2439,18 +2428,6 @@
   return allow;
 }
 
-bool ChromeContentBrowserClient::AllowSignedExchangeOnIO(
-    content::ResourceContext* resource_context) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  DCHECK(!base::FeatureList::IsEnabled(features::kNavigationLoaderOnUI));
-  // Null-check safe_browsing_service_ as in unit tests |resource_context| is a
-  // MockResourceContext and the cast doesn't work.
-  if (!safe_browsing_service_)
-    return false;
-  ProfileIOData* io_data = ProfileIOData::FromResourceContext(resource_context);
-  return io_data->signed_exchange_enabled()->GetValue();
-}
-
 bool ChromeContentBrowserClient::AllowSignedExchange(
     content::BrowserContext* browser_context) {
   DCHECK_CURRENTLY_ON(BrowserThread::UI);
@@ -4544,11 +4521,10 @@
 
 namespace {
 // TODO(jam): move this to a separate file.
-template <class HandlerRegistry>
 class ProtocolHandlerThrottle : public blink::URLLoaderThrottle {
  public:
   explicit ProtocolHandlerThrottle(
-      const HandlerRegistry& protocol_handler_registry)
+      ProtocolHandlerRegistry* protocol_handler_registry)
       : protocol_handler_registry_(protocol_handler_registry) {}
   ~ProtocolHandlerThrottle() override = default;
 
@@ -4574,122 +4550,11 @@
       *url = translated_url;
   }
 
-  HandlerRegistry protocol_handler_registry_;
+  ProtocolHandlerRegistry* protocol_handler_registry_;
 };
 }  // namespace
 
 std::vector<std::unique_ptr<blink::URLLoaderThrottle>>
-ChromeContentBrowserClient::CreateURLLoaderThrottlesOnIO(
-    const network::ResourceRequest& request,
-    content::ResourceContext* resource_context,
-    const base::RepeatingCallback<content::WebContents*()>& wc_getter,
-    content::NavigationUIData* navigation_ui_data,
-    int frame_tree_node_id) {
-  DCHECK_CURRENTLY_ON(BrowserThread::IO);
-  // TODO(falken): Uncomment out the DCHECK when PlzWorker is moved to the UI
-  // thread.
-  // DCHECK(!base::FeatureList::IsEnabled(features::kNavigationLoaderOnUI));
-
-  std::vector<std::unique_ptr<blink::URLLoaderThrottle>> result;
-
-  ProfileIOData* io_data = nullptr;
-  // Only set |io_data| if needed, as in unit tests |resource_context| is a
-  // MockResourceContext and the cast doesn't work.
-  if (safe_browsing_service_ ||
-      data_reduction_proxy::params::IsEnabledWithNetworkService()) {
-    io_data = ProfileIOData::FromResourceContext(resource_context);
-  }
-
-  ChromeNavigationUIData* chrome_navigation_ui_data =
-      static_cast<ChromeNavigationUIData*>(navigation_ui_data);
-  if (chrome_navigation_ui_data && io_data &&
-      io_data->data_reduction_proxy_io_data() &&
-      data_reduction_proxy::params::IsEnabledWithNetworkService()) {
-    if (!data_reduction_proxy_throttle_manager_) {
-      data_reduction_proxy_throttle_manager_ = std::unique_ptr<
-          data_reduction_proxy::DataReductionProxyThrottleManager,
-          base::OnTaskRunnerDeleter>(
-          new data_reduction_proxy::DataReductionProxyThrottleManager(
-              io_data->data_reduction_proxy_io_data(),
-              io_data->data_reduction_proxy_io_data()->CreateThrottleConfig()),
-          base::OnTaskRunnerDeleter(base::SequencedTaskRunnerHandle::Get()));
-    }
-    net::HttpRequestHeaders headers;
-    data_reduction_proxy::DataReductionProxyRequestOptions* request_options =
-        io_data->data_reduction_proxy_io_data()->request_options();
-    uint64_t page_id =
-        base::FeatureList::IsEnabled(
-            data_reduction_proxy::features::
-                kDataReductionProxyPopulatePreviewsPageIDToPingback)
-            ? chrome_navigation_ui_data->data_reduction_proxy_page_id()
-            : request_options->GeneratePageId();
-    request_options->AddPageIDRequestHeader(&headers, page_id);
-    result.push_back(std::make_unique<
-                     data_reduction_proxy::DataReductionProxyURLLoaderThrottle>(
-        headers, data_reduction_proxy_throttle_manager_.get()));
-  }
-
-#if BUILDFLAG(SAFE_BROWSING_DB_LOCAL) || BUILDFLAG(SAFE_BROWSING_DB_REMOTE)
-  if (io_data && safe_browsing_service_) {
-    bool matches_enterprise_whitelist = safe_browsing::IsURLWhitelistedByPolicy(
-        request.url, io_data->safe_browsing_whitelist_domains());
-    if (!matches_enterprise_whitelist) {
-      result.push_back(safe_browsing::BrowserURLLoaderThrottle::Create(
-          base::BindOnce(
-              &ChromeContentBrowserClient::GetSafeBrowsingUrlCheckerDelegate,
-              base::Unretained(this)),
-          wc_getter, frame_tree_node_id, resource_context));
-    }
-  }
-#endif
-
-  if (chrome_navigation_ui_data &&
-      chrome_navigation_ui_data->prerender_mode() != prerender::NO_PRERENDER) {
-    result.push_back(std::make_unique<prerender::PrerenderURLLoaderThrottle>(
-        chrome_navigation_ui_data->prerender_mode(),
-        chrome_navigation_ui_data->prerender_histogram_prefix(),
-        base::BindOnce(GetPrerenderCanceller, wc_getter),
-        base::CreateSingleThreadTaskRunnerWithTraits({BrowserThread::UI})));
-  }
-
-  if (io_data) {
-    bool is_off_the_record = io_data->IsOffTheRecord();
-    bool is_signed_in =
-        !is_off_the_record &&
-        !io_data->google_services_account_id()->GetValue().empty();
-
-    chrome::mojom::DynamicParams dynamic_params = {
-        io_data->force_google_safesearch()->GetValue(),
-        io_data->force_youtube_restrict()->GetValue(),
-        io_data->allowed_domains_for_apps()->GetValue(),
-        variations::VariationsHttpHeaderProvider::GetInstance()
-            ->GetClientDataHeader(is_signed_in)};
-    result.push_back(std::make_unique<GoogleURLLoaderThrottle>(
-        is_off_the_record, std::move(dynamic_params)));
-
-    result.push_back(
-        std::make_unique<ProtocolHandlerThrottle<
-            scoped_refptr<ProtocolHandlerRegistry::IOThreadDelegate>>>(
-            io_data->protocol_handler_registry_io_thread_delegate()));
-  }
-
-#if BUILDFLAG(ENABLE_PLUGINS)
-  result.push_back(std::make_unique<PluginResponseInterceptorURLLoaderThrottle>(
-      resource_context, request.resource_type, frame_tree_node_id));
-#endif
-
-  auto delegate =
-      std::make_unique<signin::HeaderModificationDelegateOnIOThreadImpl>(
-          resource_context);
-  auto signin_throttle = signin::URLLoaderThrottle::MaybeCreate(
-      std::move(delegate), navigation_ui_data, wc_getter);
-  if (signin_throttle)
-    result.push_back(std::move(signin_throttle));
-
-  return result;
-}
-
-std::vector<std::unique_ptr<blink::URLLoaderThrottle>>
 ChromeContentBrowserClient::CreateURLLoaderThrottles(
     const network::ResourceRequest& request,
     content::BrowserContext* browser_context,
@@ -4767,10 +4632,8 @@
   result.push_back(std::make_unique<GoogleURLLoaderThrottle>(
       is_off_the_record, std::move(dynamic_params)));
 
-  result.push_back(
-      std::make_unique<ProtocolHandlerThrottle<ProtocolHandlerRegistry*>>(
-          ProtocolHandlerRegistryFactory::GetForBrowserContext(
-              browser_context)));
+  result.push_back(std::make_unique<ProtocolHandlerThrottle>(
+      ProtocolHandlerRegistryFactory::GetForBrowserContext(browser_context)));
 
 #if BUILDFLAG(ENABLE_PLUGINS)
   result.push_back(std::make_unique<PluginResponseInterceptorURLLoaderThrottle>(
@@ -5295,24 +5158,6 @@
   return content::OverlayWindow::Create(controller);
 }
 
-bool ChromeContentBrowserClient::IsSafeRedirectTargetOnIO(
-    const GURL& url,
-    content::ResourceContext* context) {
-  DCHECK(!base::FeatureList::IsEnabled(features::kNavigationLoaderOnUI));
-#if BUILDFLAG(ENABLE_EXTENSIONS)
-  if (url.SchemeIs(extensions::kExtensionScheme)) {
-    ProfileIOData* io_data = ProfileIOData::FromResourceContext(context);
-    const Extension* extension =
-        io_data->GetExtensionInfoMap()->extensions().GetByID(url.host());
-    if (!extension)
-      return false;
-    return extensions::WebAccessibleResourcesInfo::IsResourceWebAccessible(
-        extension, url.path());
-  }
-#endif  // BUILDFLAG(ENABLE_EXTENSIONS)
-  return true;
-}
-
 bool ChromeContentBrowserClient::IsSafeRedirectTarget(
     const GURL& url,
     content::BrowserContext* context) {
diff --git a/chrome/browser/chrome_content_browser_client.h b/chrome/browser/chrome_content_browser_client.h
index 1b4fd9d..0b9c225 100644
--- a/chrome/browser/chrome_content_browser_client.h
+++ b/chrome/browser/chrome_content_browser_client.h
@@ -217,9 +217,6 @@
   void UpdateRendererPreferencesForWorker(
       content::BrowserContext* browser_context,
       blink::mojom::RendererPreferences* out_prefs) override;
-  bool AllowAppCacheOnIO(const GURL& manifest_url,
-                         const GURL& first_party,
-                         content::ResourceContext* context) override;
   bool AllowAppCache(const GURL& manifest_url,
                      const GURL& first_party,
                      content::BrowserContext* context) override;
@@ -236,8 +233,6 @@
                          content::BrowserContext* context,
                          int render_process_id,
                          int render_frame_id) override;
-  bool AllowSignedExchangeOnIO(
-      content::ResourceContext* resource_context) override;
   bool AllowSignedExchange(content::BrowserContext* browser_context) override;
   void AllowWorkerFileSystem(
       const GURL& url,
@@ -442,13 +437,6 @@
   base::FilePath GetLoggingFileName(
       const base::CommandLine& command_line) override;
   std::vector<std::unique_ptr<blink::URLLoaderThrottle>>
-  CreateURLLoaderThrottlesOnIO(
-      const network::ResourceRequest& request,
-      content::ResourceContext* resource_context,
-      const base::RepeatingCallback<content::WebContents*()>& wc_getter,
-      content::NavigationUIData* navigation_ui_data,
-      int frame_tree_node_id) override;
-  std::vector<std::unique_ptr<blink::URLLoaderThrottle>>
   CreateURLLoaderThrottles(
       const network::ResourceRequest& request,
       content::BrowserContext* browser_context,
@@ -545,8 +533,6 @@
       network::mojom::URLLoaderFactoryPtr* out_factory) override;
   std::unique_ptr<content::OverlayWindow> CreateWindowForPictureInPicture(
       content::PictureInPictureWindowController* controller) override;
-  bool IsSafeRedirectTargetOnIO(const GURL& url,
-                                content::ResourceContext* context) override;
   bool IsSafeRedirectTarget(const GURL& url,
                             content::BrowserContext* context) override;
   void RegisterRendererPreferenceWatcher(
diff --git a/chrome/browser/offline_pages/offline_page_request_handler.cc b/chrome/browser/offline_pages/offline_page_request_handler.cc
index 4b41389..daf99a9 100644
--- a/chrome/browser/offline_pages/offline_page_request_handler.cc
+++ b/chrome/browser/offline_pages/offline_page_request_handler.cc
@@ -31,7 +31,6 @@
 #include "content/public/browser/browser_task_traits.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/web_contents.h"
-#include "content/public/common/content_features.h"
 #include "content/public/common/resource_type.h"
 #include "net/base/file_stream.h"
 #include "net/base/filename_util.h"
@@ -77,12 +76,6 @@
 // Consistent with the buffer size used in url request data reading.
 const size_t kMaxBufferSizeForValidation = 4096;
 
-content::BrowserThread::ID GetJobThreadID() {
-  return base::FeatureList::IsEnabled(features::kNavigationLoaderOnUI)
-             ? content::BrowserThread::UI
-             : content::BrowserThread::IO;
-}
-
 void GetFileSize(const base::FilePath& file_path, int64_t* file_size) {
   bool succeeded = base::GetFileSize(file_path, file_size);
   if (!succeeded) {
@@ -262,31 +255,14 @@
                       : nullptr;
 }
 
-void NotifyAvailableOfflinePagesOnJobThread(
-    base::WeakPtr<OfflinePageRequestHandler> job,
-    const std::vector<OfflinePageRequestHandler::Candidate>& candidates) {
-  DCHECK_CURRENTLY_ON(GetJobThreadID());
-
-  if (job)
-    job->OnOfflinePagesAvailable(candidates);
-}
-
 // Notifies OfflinePageRequestHandler about all the matched offline pages.
 void NotifyAvailableOfflinePagesOnUI(
     base::WeakPtr<OfflinePageRequestHandler> job,
     const std::vector<OfflinePageRequestHandler::Candidate>& candidates) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
 
-  if (base::FeatureList::IsEnabled(features::kNavigationLoaderOnUI)) {
-    NotifyAvailableOfflinePagesOnJobThread(job, candidates);
-  } else {
-    // Delegates to IO thread since OfflinePageRequestHandler should only be
-    // accessed from IO thread.
-    base::PostTaskWithTraits(
-        FROM_HERE, {content::BrowserThread::IO},
-        base::BindOnce(&NotifyAvailableOfflinePagesOnJobThread, job,
-                       candidates));
-  }
+  if (job)
+    job->OnOfflinePagesAvailable(candidates);
 }
 
 // Failed to find an offline page.
@@ -487,7 +463,7 @@
       network_state_(NetworkState::CONNECTED_NETWORK),
       candidate_index_(0),
       weak_ptr_factory_(this) {
-  DCHECK_CURRENTLY_ON(GetJobThreadID());
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
   std::string offline_header_value;
   extra_request_headers.GetHeader(kOfflinePageHeader, &offline_header_value);
   // Note that |offline_header| will be empty if parsing from the header value
@@ -499,7 +475,7 @@
 
 OfflinePageRequestHandler::NetworkState
 OfflinePageRequestHandler::GetNetworkState() const {
-  DCHECK_CURRENTLY_ON(GetJobThreadID());
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
 
   if (offline_header_.reason == OfflinePageHeader::Reason::NET_ERROR)
     return OfflinePageRequestHandler::NetworkState::FLAKY_NETWORK;
diff --git a/chrome/browser/offline_pages/offline_page_request_handler_unittest.cc b/chrome/browser/offline_pages/offline_page_request_handler_unittest.cc
index 48ab504a..067b590c 100644
--- a/chrome/browser/offline_pages/offline_page_request_handler_unittest.cc
+++ b/chrome/browser/offline_pages/offline_page_request_handler_unittest.cc
@@ -9,7 +9,6 @@
 
 #include "base/bind.h"
 #include "base/callback.h"
-#include "base/feature_list.h"
 #include "base/files/file_path.h"
 #include "base/files/file_util.h"
 #include "base/memory/weak_ptr.h"
@@ -40,7 +39,6 @@
 #include "content/public/browser/browser_task_traits.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/web_contents.h"
-#include "content/public/common/content_features.h"
 #include "content/public/common/previews_state.h"
 #include "content/public/common/resource_type.h"
 #include "content/public/test/test_browser_thread_bundle.h"
@@ -97,14 +95,6 @@
 
 const int64_t kDownloadId = 42LL;
 
-// Returns the thread the navigation URL loader will run on. This determines
-// where the OfflinePageURLLoader should be created.
-content::BrowserThread::ID GetNavigationLoaderThreadID() {
-  return base::FeatureList::IsEnabled(features::kNavigationLoaderOnUI)
-             ? content::BrowserThread::UI
-             : content::BrowserThread::IO;
-}
-
 struct ResponseInfo {
   explicit ResponseInfo(int request_status) : request_status(request_status) {
     DCHECK_NE(net::OK, request_status);
@@ -270,16 +260,15 @@
 
  private:
   void OnHandleReady(MojoResult result, const mojo::HandleSignalsState& state);
-  void InterceptRequestOnLoaderThread(
-      const GURL& url,
-      const std::string& method,
-      const net::HttpRequestHeaders& extra_headers,
-      bool is_main_frame);
+  void InterceptRequestInternal(const GURL& url,
+                                const std::string& method,
+                                const net::HttpRequestHeaders& extra_headers,
+                                bool is_main_frame);
   void MaybeStartLoader(
       const network::ResourceRequest& request,
       content::URLLoaderRequestInterceptor::RequestHandler request_handler);
   void ReadBody();
-  void ReadCompletedOnLoaderThread(const ResponseInfo& response);
+  void ReadCompleted(const ResponseInfo& response);
 
   OfflinePageRequestHandlerTest* test_;
   std::unique_ptr<ChromeNavigationUIData> navigation_ui_data_;
@@ -950,8 +939,8 @@
 
 void OfflinePageURLLoaderBuilder::OnReceiveRedirect(
     const GURL& redirected_url) {
-  InterceptRequestOnLoaderThread(redirected_url, "GET",
-                                 net::HttpRequestHeaders(), true);
+  InterceptRequestInternal(redirected_url, "GET", net::HttpRequestHeaders(),
+                           true);
 }
 
 void OfflinePageURLLoaderBuilder::OnReceiveResponse(
@@ -968,19 +957,19 @@
     mime_type_.clear();
     body_.clear();
   }
-  ReadCompletedOnLoaderThread(
+  ReadCompleted(
       ResponseInfo(client_->completion_status().error_code, mime_type_, body_));
   // Clear intermediate data in preparation for next potential page loading.
   mime_type_.clear();
   body_.clear();
 }
 
-void OfflinePageURLLoaderBuilder::InterceptRequestOnLoaderThread(
+void OfflinePageURLLoaderBuilder::InterceptRequestInternal(
     const GURL& url,
     const std::string& method,
     const net::HttpRequestHeaders& extra_headers,
     bool is_main_frame) {
-  DCHECK_CURRENTLY_ON(GetNavigationLoaderThreadID());
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
 
   client_ = std::make_unique<TestURLLoaderClient>(this);
 
@@ -1009,26 +998,17 @@
     const net::HttpRequestHeaders& extra_headers,
     bool is_main_frame) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
-
-  if (GetNavigationLoaderThreadID() == content::BrowserThread::UI) {
-    InterceptRequestOnLoaderThread(url, method, extra_headers, is_main_frame);
-  } else {
-    base::PostTaskWithTraits(
-        FROM_HERE, {content::BrowserThread::IO},
-        base::BindOnce(
-            &OfflinePageURLLoaderBuilder::InterceptRequestOnLoaderThread,
-            base::Unretained(this), url, method, extra_headers, is_main_frame));
-  }
+  InterceptRequestInternal(url, method, extra_headers, is_main_frame);
   base::RunLoop().Run();
 }
 
 void OfflinePageURLLoaderBuilder::MaybeStartLoader(
     const network::ResourceRequest& request,
     content::URLLoaderRequestInterceptor::RequestHandler request_handler) {
-  DCHECK_CURRENTLY_ON(GetNavigationLoaderThreadID());
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
 
   if (!request_handler) {
-    ReadCompletedOnLoaderThread(ResponseInfo(net::ERR_FAILED));
+    ReadCompleted(ResponseInfo(net::ERR_FAILED));
     return;
   }
 
@@ -1063,7 +1043,7 @@
 
     // The pipe was closed.
     if (rv == MOJO_RESULT_FAILED_PRECONDITION) {
-      ReadCompletedOnLoaderThread(ResponseInfo(net::ERR_FAILED));
+      ReadCompleted(ResponseInfo(net::ERR_FAILED));
       return;
     }
 
@@ -1078,15 +1058,14 @@
     MojoResult result,
     const mojo::HandleSignalsState& state) {
   if (result != MOJO_RESULT_OK) {
-    ReadCompletedOnLoaderThread(ResponseInfo(net::ERR_FAILED));
+    ReadCompleted(ResponseInfo(net::ERR_FAILED));
     return;
   }
   ReadBody();
 }
 
-void OfflinePageURLLoaderBuilder::ReadCompletedOnLoaderThread(
-    const ResponseInfo& response) {
-  DCHECK_CURRENTLY_ON(GetNavigationLoaderThreadID());
+void OfflinePageURLLoaderBuilder::ReadCompleted(const ResponseInfo& response) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
 
   handle_watcher_.reset();
   client_.reset();
@@ -1099,15 +1078,7 @@
   if (offline_page_data && offline_page_data->is_offline_page())
     is_offline_page_set_in_navigation_data = true;
 
-  if (GetNavigationLoaderThreadID() == content::BrowserThread::UI) {
-    test()->ReadCompleted(response, is_offline_page_set_in_navigation_data);
-  } else {
-    base::PostTaskWithTraits(
-        FROM_HERE, {content::BrowserThread::UI},
-        base::BindOnce(&OfflinePageRequestHandlerTest::ReadCompleted,
-                       base::Unretained(test()), response,
-                       is_offline_page_set_in_navigation_data));
-  }
+  test()->ReadCompleted(response, is_offline_page_set_in_navigation_data);
 }
 
 TEST_F(OfflinePageRequestHandlerTest, FailedToCreateRequestJob) {
diff --git a/chrome/browser/prerender/prerender_nostate_prefetch_browsertest.cc b/chrome/browser/prerender/prerender_nostate_prefetch_browsertest.cc
index 1585e08..fc6bebf 100644
--- a/chrome/browser/prerender/prerender_nostate_prefetch_browsertest.cc
+++ b/chrome/browser/prerender/prerender_nostate_prefetch_browsertest.cc
@@ -37,7 +37,6 @@
 #include "content/public/browser/render_frame_host.h"
 #include "content/public/browser/render_process_host.h"
 #include "content/public/browser/storage_partition.h"
-#include "content/public/common/content_features.h"
 #include "content/public/common/result_codes.h"
 #include "content/public/common/url_constants.h"
 #include "content/public/test/browser_test_utils.h"
@@ -130,16 +129,8 @@
             ->GetAppCacheService();
     do {
       base::RunLoop wait_loop;
-      if (base::FeatureList::IsEnabled(features::kNavigationLoaderOnUI)) {
-        WaitForAppcacheOnLoaderThread(manifest_url, appcache_service,
-                                      base::DoNothing(), &found_manifest);
-      } else {
-        base::PostTaskWithTraits(
-            FROM_HERE, {content::BrowserThread::IO},
-            base::BindOnce(WaitForAppcacheOnLoaderThread, manifest_url,
-                           appcache_service, wait_loop.QuitClosure(),
-                           &found_manifest));
-      }
+      WaitForAppcache(manifest_url, appcache_service, base::DoNothing(),
+                      &found_manifest);
       // There seems to be some flakiness in the appcache getting back to us, so
       // use a timeout task to try the appcache query again.
       base::PostDelayedTaskWithTraits(FROM_HERE, {content::BrowserThread::UI},
@@ -185,11 +176,10 @@
   // |found_manifest| if an appcache exists for |manifest_url|. |callback| will
   // be called on the UI thread after the info is retrieved, whether or not the
   // manifest exists.
-  static void WaitForAppcacheOnLoaderThread(
-      const GURL& manifest_url,
-      content::AppCacheService* appcache_service,
-      base::Closure callback,
-      bool* found_manifest) {
+  static void WaitForAppcache(const GURL& manifest_url,
+                              content::AppCacheService* appcache_service,
+                              base::Closure callback,
+                              bool* found_manifest) {
     scoped_refptr<content::AppCacheInfoCollection> info_collection =
         new content::AppCacheInfoCollection();
     appcache_service->GetAllAppCacheInfo(