Add stats collection for telemetry startup.warm.blank_page test.

components/startup_metric_utils/startup_metric_utils.h

 // Copyright 2013 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.
 
 #ifndef COMPONENTS_STARTUP_METRIC_UTILS_STARTUP_METRIC_UTILS_H_
 #define COMPONENTS_STARTUP_METRIC_UTILS_STARTUP_METRIC_UTILS_H_
 
 #include <string>
 
 #include "base/time/time.h"
 
 // Utility functions to support metric collection for browser startup.
 
 namespace startup_metric_utils {
 
 // Returns true if any UI other than the browser window has been displayed
 // so far.  Useful to test if UI has been displayed before the first browser
 // window was shown, which would invalidate any surrounding timing metrics.
 bool WasNonBrowserUIDisplayed();
 
 // Call this when displaying UI that might potentially delay the appearance
 // of the initial browser window on Chrome startup.
 //
 // Note on usage: This function is idempotent and its overhead is low enough
 // in comparison with UI display that it's OK to call it on every
 // UI invocation regardless of whether the browser window has already
 // been displayed or not.
 void SetNonBrowserUIDisplayed();
 
-// Call this as early as possible in the startup process to record a
-// timestamp.
+// Call this as early as possible in the startup process to record a timestamp.
 void RecordMainEntryPointTime();
 
 // Call this when the executable is loaded and main() is entered. Can be
 // different from |RecordMainEntryPointTime| when the startup process is
 // contained in a separate dll, such as with chrome.exe / chrome.dll on Windows.
 void RecordExeMainEntryTime();
 
-#if defined(OS_ANDROID)
-// On Android the entry point time is the time at which the Java code starts.
-// This is recorded on the Java side, and then passed to the C++ side once the
-// C++ library is loaded and running.
+// Call this with a previously recorded timestamp if unable to call
+// RecordMainEntryPointTime() directly on startup.
+// On Android, the entry point time is the time at which the Java code starts.
+// In Mojo, the entry point time is the time at which the shell starts.
 void RecordSavedMainEntryPointTime(const base::Time& entry_point_time);
-#endif // OS_ANDROID
 
 // Called just before the message loop is about to start. Entry point to record
 // startup stats.
 // |is_first_run| - is the current launch part of a first run.
 void OnBrowserStartupComplete(bool is_first_run);
 
 // Returns the time of main entry recorded from RecordMainEntryPointTime.
 // Returns NULL if that method has not yet been called.
 // This method is expected to be called from the UI thread.
 const base::Time* MainEntryPointTime();
 
 }  // namespace startup_metric_utils
 
 #endif  // COMPONENTS_STARTUP_METRIC_UTILS_STARTUP_METRIC_UTILS_H_