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 <stdint.h>
 #include <string>
 
 #include "base/time/time.h"
 #include "build/build_config.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.
@@ skipping 11 matching lines @@
   // This must be last.
   STARTUP_TEMPERATURE_MAX
 };
 
 #if defined(OS_WIN)
 // Gets the hard fault count of the current process through |hard_fault_count|.
 // Returns true on success.
 bool GetHardFaultCountForCurrentProcess(uint32_t* hard_fault_count);
 #endif  // defined(OS_WIN)
 
+// Registers startup metric 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 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 a renderer main entry time. The value provided for the first
 // call to this function is used to compute
 // Startup.LoadTime.BrowserMainToRendererMain. Further calls to this
 // function are ignored.
@@ skipping 21 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_