Allow overlapping sync and async startup requests

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"
@@ skipping 14 matching lines @@
 }
 
 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());
+    // 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
+    // browser runner for the second request.
+    if (!browser_runner_.get()) {
+      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);
 }