android: Fix java launcher thread

content/browser/browser_main_loop.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 "content/browser/browser_main_loop.h"
 
 #include <stddef.h>
 
 #include <string>
 #include <utility>
@@ skipping 1051 matching lines @@
       case BrowserThread::PROCESS_LAUNCHER:
         TRACE_EVENT_BEGIN1("startup",
             "BrowserMainLoop::CreateThreads:start",
             "Thread", "BrowserThread::PROCESS_LAUNCHER");
 #if defined(OS_ANDROID)
         // Android specializes Launcher thread so it is accessible in java.
         // Note Android never does clean shutdown, so shutdown use-after-free
         // concerns are not a problem in practice.
         redirect_thread = false;
         message_loop = android::LauncherThread::GetMessageLoop();
+        DCHECK(message_loop);
 #endif
         if (redirect_thread) {
           non_ui_non_io_task_runner_traits
               .WithPriority(base::TaskPriority::USER_BLOCKING)
               .WithShutdownBehavior(base::TaskShutdownBehavior::BLOCK_SHUTDOWN);
         } else {
           thread_to_start = &process_launcher_thread_;
           options.timer_slack = base::TIMER_SLACK_MAXIMUM;
         }
         break;
@@ skipping 38 matching lines @@
         NOTREACHED();
         break;
     }
 
     BrowserThread::ID id = static_cast<BrowserThread::ID>(thread_id);
 
     if (thread_to_start) {
       (*thread_to_start)
           .reset(message_loop ? new BrowserProcessSubThread(id, message_loop)
                               : new BrowserProcessSubThread(id));
-      if (!(*thread_to_start)->StartWithOptions(options))
+      // Start the thread if an existing |message_loop| wasn't provided.
+      if (!message_loop && !(*thread_to_start)->StartWithOptions(options))
         LOG(FATAL) << "Failed to start the browser thread: id == " << id;
     } else {
       scoped_refptr<base::SingleThreadTaskRunner> redirection_task_runner =
           base::CreateSingleThreadTaskRunnerWithTraits(
               non_ui_non_io_task_runner_traits);
       DCHECK(redirection_task_runner);
       BrowserThreadImpl::RedirectThreadIDToTaskRunner(
           id, std::move(redirection_task_runner));
     }
 
@@ skipping 616 matching lines @@
         BrowserThread::GetTaskRunnerForThread(BrowserThread::FILE),
         MediaInternals::GetInstance());
   }
   CHECK(audio_manager_);
 
   audio_system_ = media::AudioSystemImpl::Create(audio_manager_.get());
   CHECK(audio_system_);
 }
 
 }  // namespace content