Run the later parts of startup as UI thread tasks

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 "base/memory/scoped_ptr.h"
 #include "chrome/browser/android/chrome_jni_registrar.h"
 #include "chrome/browser/android/chrome_startup_flags.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()
+    : incremental_startup_enabled_(false) {}
 
 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);
 
     browser_runner_.reset(content::BrowserMainRunner::Create());
-    return browser_runner_->Initialize(main_function_params);
+
+    // For Chrome on android we want to run the startup tasks incrementally, so
+    // that UI tasks can get in in-between.
+    content::StartupTaskRunner::StartupMode mode =
+        incremental_startup_enabled_ ? content::StartupTaskRunner::INCREMENTAL
+                                     : content::StartupTaskRunner::IMMEDIATE;
+    scoped_refptr<content::StartupTaskRunner> startup_task_runner(
+        new content::StartupTaskRunner(mode, GetStartupObserver()));
+
+    return browser_runner_->Initialize(main_function_params,
+                                       startup_task_runner);
   }
 
   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);
 }
+
+void ChromeMainDelegateAndroid::EnableIncrementalStartup(bool enable) {
+  incremental_startup_enabled_ = enable;
+}