Re-enable pre-read experiment as a finch field trial.

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 348 matching lines @@
   return NULL;
 }
 
 #if defined(OS_MACOSX)
 OSStatus KeychainCallback(SecKeychainEvent keychain_event,
                           SecKeychainCallbackInfo* info, void* context) {
   return noErr;
 }
 #endif
 
-// This code is specific to the Windows-only PreReadExperiment field-trial.
-void AddPreReadHistogramTime(const char* name, base::TimeDelta time) {
-  const base::TimeDelta kMin(base::TimeDelta::FromMilliseconds(1));
-  const base::TimeDelta kMax(base::TimeDelta::FromHours(1));
-  static const size_t kBuckets(100);
-
-  // FactoryTimeGet will always return a pointer to the same histogram object,
-  // keyed on its name. There's no need for us to store it explicitly anywhere.
-  base::HistogramBase* counter = base::Histogram::FactoryTimeGet(
-      name, kMin, kMax, kBuckets, base::Histogram::kUmaTargetedHistogramFlag);
-
-  counter->AddTime(time);
-}
-
 void RegisterComponentsForUpdate(const CommandLine& command_line) {
   ComponentUpdateService* cus = g_browser_process->component_updater();
 
   // Registration can be before or after cus->Start() so it is ok to post
   // a task to the UI thread to do registration once you done the necessary
   // file IO to know you existing component version.
 #if !defined(OS_CHROMEOS)
   RegisterRecoveryComponent(cus, g_browser_process->local_state());
   RegisterPepperFlashComponent(cus);
   RegisterSwiftShaderComponent(cus);
@@ skipping 295 matching lines @@
 
   bool is_first_run = first_run::IsChromeFirstRun();
 
 // CurrentProcessInfo::CreationTime() is currently only implemented on some
 // platforms.
 #if defined(OS_MACOSX) || defined(OS_WIN) || defined(OS_LINUX)
   const base::Time process_creation_time =
       base::CurrentProcessInfo::CreationTime();
 
   if (!is_first_run && !process_creation_time.is_null()) {
-    RecordPreReadExperimentTime("Startup.BrowserMessageLoopStartTime",
-        base::Time::Now() - process_creation_time);
+    base::TimeDelta delay = base::Time::Now() - process_creation_time;
+    UMA_HISTOGRAM_LONG_TIMES_100("Startup.BrowserMessageLoopStartTime", delay);
   }
 #endif  // defined(OS_MACOSX) || defined(OS_WIN) || defined(OS_LINUX)
 
   // 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,
-                                                         base::TimeDelta time) {
-  DCHECK(name != NULL);
-
-  // This gets called with different histogram names, so we don't want to use
-  // the UMA_HISTOGRAM_CUSTOM_TIMES macro--it uses a static variable, and the
-  // first call wins.
-  AddPreReadHistogramTime(name, time);
-
-#if defined(OS_WIN)
-#if defined(GOOGLE_CHROME_BUILD)
-  // The pre-read experiment is Windows and Google Chrome specific.
-  scoped_ptr<base::Environment> env(base::Environment::Create());
-
-  // Only record the sub-histogram result if the experiment is running
-  // (environment variable is set, and valid).
-  std::string pre_read_percentage;
-  if (env->GetVar(chrome::kPreReadEnvironmentVariable, &pre_read_percentage)) {
-    std::string uma_name(name);
-
-    // We want XP to record a separate histogram, as the loader on XP
-    // is very different from the Vista and Win7 loaders.
-    if (base::win::GetVersion() <= base::win::VERSION_XP)
-      uma_name += "_XP";
-
-    uma_name += "_PreRead_";
-    uma_name += pre_read_percentage;
-    AddPreReadHistogramTime(uma_name.c_str(), time);
-  }
-#endif
-#endif
-}
-
 // -----------------------------------------------------------------------------
 // TODO(viettrungluu): move more/rest of BrowserMain() into BrowserMainParts.
 
 #if defined(OS_WIN)
 #define DLLEXPORT __declspec(dllexport)
 
 // We use extern C for the prototype DLLEXPORT to avoid C++ name mangling.
 extern "C" {
 DLLEXPORT void __cdecl RelaunchChromeBrowserWithNewCommandLineIfNeeded();
 }
@@ skipping 792 matching lines @@
     // Record now as the last successful chrome start.
     GoogleUpdateSettings::SetLastRunTime();
 
 #if defined(OS_MACOSX)
     // Call Recycle() here as late as possible, before going into the loop
     // because Start() will add things to it while creating the main window.
     if (parameters().autorelease_pool)
       parameters().autorelease_pool->Recycle();
 #endif
 
-    RecordPreReadExperimentTime("Startup.BrowserOpenTabs",
-                                base::TimeTicks::Now() - browser_open_start);
+    base::TimeTicks browser_open_end = base::TimeTicks::Now();
+    base::TimeDelta browser_open_delta = browser_open_end - browser_open_start;

[Alexei Svitkine (slow), 2013/09/03 18:48:45]

Nit: Inline base::TimeTicks::Now(), e.g.:

    base::TimeDelta startup_time = base::TimeTicks::Now() - browser_open_start;

[Roger McFarlane (Chromium), 2013/09/03 19:32:10]

Done.

+    UMA_HISTOGRAM_LONG_TIMES_100("Startup.BrowserOpenTabs", browser_open_delta);
 
     // If we're running tests (ui_task is non-null), then we don't want to
     // call FetchLanguageListFromTranslateServer or
     // StartRepeatedVariationsSeedFetch.
     if (parameters().ui_task == NULL) {
       // Request new variations seed information from server.
       chrome_variations::VariationsService* variations_service =
           browser_process_->variations_service();
       if (variations_service) {
         variations_service->StartRepeatedVariationsSeedFetch();
@@ skipping 132 matching lines @@
   chromeos::CrosSettings::Shutdown();
 #endif
 #endif
 }
 
 // Public members:
 
 void ChromeBrowserMainParts::AddParts(ChromeBrowserMainExtraParts* parts) {
   chrome_extra_parts_.push_back(parts);
 }