Implement CurrentProcessInfo::CreationTime() for Linux.

chrome/browser/chrome_browser_main.cc

 // 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.
 
 #include "chrome/browser/chrome_browser_main.h"
 
 #if defined(TOOLKIT_GTK)
 #include <gtk/gtk.h>
 #endif
 
@@ skipping 671 matching lines @@
 }
 
 void ChromeBrowserMainParts::RecordBrowserStartupTime() {
   // Don't record any metrics if UI was displayed before this point e.g.
   // warning dialogs.
   if (startup_metric_utils::WasNonBrowserUIDisplayed())
     return;
 
   bool is_first_run = first_run::IsChromeFirstRun();
 
-// CurrentProcessInfo::CreationTime() is currently only implemented on Mac and
-// Windows.
-#if defined(OS_MACOSX) || defined(OS_WIN)
   const base::Time* process_creation_time =
       base::CurrentProcessInfo::CreationTime();
 
   if (!is_first_run && process_creation_time) {
     RecordPreReadExperimentTime("Startup.BrowserMessageLoopStartTime",
         base::Time::Now() - *process_creation_time);
   }
-#endif  // defined(OS_MACOSX) || defined(OS_WIN)
 
   // Record collected startup metrics.
   startup_metric_utils::OnBrowserStartupComplete(is_first_run);
 
   // Deletes self.
   new LoadCompleteListener();
 }
 
 // This code is specific to the Windows-only PreReadExperiment field-trial.
 void ChromeBrowserMainParts::RecordPreReadExperimentTime(const char* name,
@@ skipping 988 matching lines @@
   chromeos::CrosSettings::Shutdown();
 #endif
 #endif
 }
 
 // Public members:
 
 void ChromeBrowserMainParts::AddParts(ChromeBrowserMainExtraParts* parts) {
   chrome_extra_parts_.push_back(parts);
 }