services/tracing/public/interfaces/tracing.mojom

// Copyright 2014 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.

module tracing;

// To participate in the tracing ecosystem, implement the TraceProvider
// interface and connect to the tracing app. Then, when the provider's Start()
// function is called collect tracing data and pass it back via the provided
// TraceRecorder interface up until Stop() is called.

interface TraceProvider {
  // Categories can either be the empty string to mean the default set of
  // categories or a comma-delimited list of categories to trace.
  StartTracing(string categories, TraceRecorder recorder);
  StopTracing();
};

interface TraceRecorder {
  Record(string json);
};

interface TraceCollector {
  // Request tracing data from all connected providers to stream to
  // |stream|.
  Start(handle<data_pipe_producer> stream, string categories);

  // Stop tracing and flush results to the |stream| passed in to Start().
  // Closes |stream| when all data is collected.
  StopAndFlush();
};

// These times are used to determine startup performance metrics.
// TODO(msw): Find a way to convert *_time metrics into TimeTicks earlier (ref:
// https://goo.gl/vZ8dZW).
struct StartupPerformanceTimes {
  // TODO(msw): Rename to match "BrowserMainEntryTimeAbsolute" metric?
  int64 shell_process_creation_time;
  int64 shell_main_entry_point_time;
  int64 browser_message_loop_start_ticks;
  int64 browser_window_display_ticks;
  int64 browser_open_tabs_time_delta;
  // TODO(msw): Rename to avoid "web contents"?
  int64 first_web_contents_main_frame_load_ticks;
  // TODO(msw): Rename to match "FirstWebContents.NonEmptyPaint" metric?
  int64 first_visually_non_empty_layout_ticks;
};

// This interface accepts startup performance timing from a variety of sources.
interface StartupPerformanceDataCollector {
  // These setters may be called many times, only the first time is recorded.
  SetShellProcessCreationTime(int64 time);
  SetShellMainEntryPointTime(int64 time);
  SetBrowserMessageLoopStartTicks(int64 ticks);
  SetBrowserWindowDisplayTicks(int64 ticks);
  SetBrowserOpenTabsTimeDelta(int64 delta);
  SetFirstWebContentsMainFrameLoadTicks(int64 ticks);
  SetFirstVisuallyNonEmptyLayoutTicks(int64 ticks);

  // Get the currently available startup performance times.
  GetStartupPerformanceTimes() => (StartupPerformanceTimes times);
};