[Merge M48] Add Startup.TimeSinceLastStartup histogram.

components/startup_metric_utils/browser/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_BROWSER_STARTUP_METRIC_UTILS_H_
 #define COMPONENTS_STARTUP_METRIC_UTILS_BROWSER_STARTUP_METRIC_UTILS_H_
 
 #include <string>
 
 #include "base/time/time.h"
 
+class PrefRegistrySimple;
+class PrefService;
+
 // Utility functions to support metric collection for browser startup. Timings
 // should use TimeTicks whenever possible. OS-provided timings are still
 // received as Time out of cross-platform support necessity but are converted to
 // TimeTicks as soon as possible in an attempt to reduce the potential skew
 // between the two basis. See crbug.com/544131 for reasoning.
 
 namespace startup_metric_utils {
 
 // An enumeration of startup temperatures. This must be kept in sync with the
 // UMA StartupType enumeration defined in histograms.xml.
 enum StartupTemperature {
   // The startup was a cold start: nearly all of the Chrome binaries and
   // resources were brought into memory using hard faults.
   COLD_STARTUP_TEMPERATURE = 0,
   // The startup was a warm start: the Chrome binaries and resources were
   // mostly already resident in memory and effectively no hard faults were
   // observed.
   WARM_STARTUP_TEMPERATURE = 1,
   // The startup type couldn't quite be classified as warm or cold, but rather
   // was somewhere in between.
   LUKEWARM_STARTUP_TEMPERATURE = 2,
   // This must be after all meaningful values.
   STARTUP_TEMPERATURE_COUNT,
   // Startup temperature wasn't yet determined.
   UNDETERMINED_STARTUP_TEMPERATURE
 };
 
+// Registers startup related prefs in |registry|.
+void RegisterPrefs(PrefRegistrySimple* registry);
+
 // 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
@@ skipping 12 matching lines @@
 // Call this with the time 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 RecordExeMainEntryPointTime(const base::Time& time);
 
 // Call this with the time recorded just before the message loop is started.
 // |is_first_run| - is the current launch part of a first run.
 void RecordBrowserMainMessageLoopStart(const base::TimeTicks& ticks,
                                        bool is_first_run);
 
+// Logs the Startup.TimeSinceLastStartup histogram. Obtains the timestamp of the
+// last startup from |pref_service| and overwrites it with the timestamp of the
+// current startup. If the startup temperature has been set by
+// RecordBrowserMainMessageLoopStart, the time since last startup is also logged
+// to an histogram suffixed with the startup temperature.
+void RecordTimeSinceLastStartup(PrefService* pref_service);
+
 // Call this with the time when the first browser window became visible.
 void RecordBrowserWindowDisplay(const base::TimeTicks& ticks);
 
 // Call this with the time delta that the browser spent opening its tabs.
 void RecordBrowserOpenTabsDelta(const base::TimeDelta& delta);
 
 // Call this with the time when the first web contents loaded its main frame,
 // only if the first web contents was unimpended in its attempt to do so.
 void RecordFirstWebContentsMainFrameLoad(const base::TimeTicks& ticks);
 
@@ skipping 25 matching lines @@
 base::TimeTicks MainEntryPointTicks();
 
 // Returns the startup type. This is only currently supported on the Windows
 // platform and will simply return UNCERTAIN_STARTUP_TYPE on other platforms.
 // This is only valid after a call to RecordBrowserMainMessageLoopStart().
 StartupTemperature GetStartupTemperature();
 
 }  // namespace startup_metric_utils
 
 #endif  // COMPONENTS_STARTUP_METRIC_UTILS_BROWSER_STARTUP_METRIC_UTILS_H_