[Android] Support startup histogram.

chrome/app/android/chrome_main_delegate_android.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/app/android/chrome_main_delegate_android.h"
 
 #include "base/android/jni_android.h"
 #include "base/debug/trace_event.h"
 #include "chrome/browser/android/chrome_jni_registrar.h"
 #include "chrome/browser/android/chrome_startup_flags.h"
+#include "chrome/browser/android/uma_utils.h"
+#include "chrome/common/startup_metric_utils.h"
 #include "content/public/browser/browser_main_runner.h"
 
 // ChromeMainDelegateAndroid is created when the library is loaded. It is always
 // done in the process's main Java thread. But for non browser process, e.g.
 // renderer process, it is not the native Chrome's main thread.
 ChromeMainDelegateAndroid::ChromeMainDelegateAndroid() {
 }
 
 ChromeMainDelegateAndroid::~ChromeMainDelegateAndroid() {
 }
 
 void ChromeMainDelegateAndroid::SandboxInitialized(
     const std::string& process_type) {
   ChromeMainDelegate::SandboxInitialized(process_type);
 }
 
 int ChromeMainDelegateAndroid::RunProcess(
     const std::string& process_type,
     const content::MainFunctionParams& main_function_params) {
   TRACE_EVENT0("startup", "ChromeMainDelegateAndroid::RunProcess")
   if (process_type.empty()) {
     JNIEnv* env = base::android::AttachCurrentThread();
     RegisterApplicationNativeMethods(env);
 
     // Because the browser process can be started asynchronously as a series of
-    // of UI thread tasks a second request to start it can come in while the
-    // first request is still being processed. We must keep the same
+    // UI thread tasks a second request to start it can come in while the
+    // first request is still being processed. Chrome must keep the same
     // browser runner for the second request.
+    // Also only record the start time the first time round, since this is the
+    // start time of the application, and will be same for all requests.
     if (!browser_runner_.get()) {
+      base::Time startTime = chrome::android::GetMainEntryPointTime();
+      startup_metric_utils::RecordSavedMainEntryPointTime(startTime);
       browser_runner_.reset(content::BrowserMainRunner::Create());
     }
     return browser_runner_->Initialize(main_function_params);
   }
 
   return ChromeMainDelegate::RunProcess(process_type, main_function_params);
 }
 
 bool ChromeMainDelegateAndroid::BasicStartupComplete(int* exit_code) {
   SetChromeSpecificCommandLineFlags();
   return ChromeMainDelegate::BasicStartupComplete(exit_code);
 }
 
 bool ChromeMainDelegateAndroid::RegisterApplicationNativeMethods(JNIEnv* env) {
   return chrome::android::RegisterJni(env);
 }