Record metrics for slow startups

chrome/common/startup_metric_utils.h

 // Copyright (c) 2012 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 CHROME_COMMON_STARTUP_METRIC_UTILS_H_
 #define CHROME_COMMON_STARTUP_METRIC_UTILS_H_
 
+#include <string>
+
 #include "base/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.
 void RecordMainEntryPointTime();
 
-// Return the time recorded by RecordMainEntryPointTime().
-const base::Time MainEntryStartTime();
+// Called just before the message loop is about to start. Entry point to record
+// startup stats.
+void OnBrowserStartupComplete();
+
+// Scoper that records the time period before it's destructed in a histogram
+// with the given name. The histogram is only recorded for slow chrome startups.
+// Useful for trying to figure out what parts of Chrome cause slow startup.
+class ScopedSlowStartupUMA {
+ public:
+  explicit ScopedSlowStartupUMA(const std::string& histogram_name)
+               : start_time_(base::TimeTicks::Now()),

[sky, 2013/01/14 21:54:11]

nit: indentation is off here.

+                 histogram_name_(histogram_name) {}
+
+  ~ScopedSlowStartupUMA();
+
+ private:
+  base::TimeTicks start_time_;

[sky, 2013/01/14 21:54:11]

nit: const on both of these.

+  std::string histogram_name_;
+
+  DISALLOW_COPY_AND_ASSIGN(ScopedSlowStartupUMA);
+};
 
 }  // namespace startup_metric_utils
 
 #endif  // CHROME_COMMON_STARTUP_METRIC_UTILS_H_