android: Java-based launcher thread

content/browser/browser_main_loop.cc

Index: content/browser/browser_main_loop.cc
diff --git a/content/browser/browser_main_loop.cc b/content/browser/browser_main_loop.cc
index eaacefc4b0fb3b15af05d0b013750dceb3f1b319..53d4813ac46f9a32b78a358132e507b9936dfb8d 100644
--- a/content/browser/browser_main_loop.cc
+++ b/content/browser/browser_main_loop.cc
@@ -123,6 +123,7 @@
 #include "base/android/jni_android.h"
 #include "components/tracing/common/graphics_memory_dump_provider_android.h"
 #include "content/browser/android/browser_startup_controller.h"
+#include "content/browser/android/launcher_thread.h"
 #include "content/browser/android/scoped_surface_request_manager.h"
 #include "content/browser/android/tracing_controller_android.h"
 #include "content/browser/media/android/browser_media_player_manager.h"
@@ -1007,7 +1008,7 @@ int BrowserMainLoop::CreateThreads() {
   base::Thread::Options ui_message_loop_options;
   ui_message_loop_options.message_loop_type = base::MessageLoop::TYPE_UI;
 
-  const bool redirect_nonUInonIO_browser_threads =
+  bool redirect_nonUInonIO_browser_threads =
       GetContentClient()
           ->browser()
           ->RedirectNonUINonIOBrowserThreadsToTaskScheduler();
@@ -1024,6 +1025,7 @@ int BrowserMainLoop::CreateThreads() {
     // updated away from its default.
     std::unique_ptr<BrowserProcessSubThread>* thread_to_start = nullptr;
     base::Thread::Options options;
+    base::MessageLoop* message_loop = nullptr;
 
     // Otherwise this thread ID will be backed by a SingleThreadTaskRunner using
     // |non_ui_non_io_task_runner_traits| (which can be augmented below).
@@ -1088,6 +1090,10 @@ int BrowserMainLoop::CreateThreads() {
         TRACE_EVENT_BEGIN1("startup",
             "BrowserMainLoop::CreateThreads:start",
             "Thread", "BrowserThread::PROCESS_LAUNCHER");
+#if defined(OS_ANDROID)
+        redirect_nonUInonIO_browser_threads = false;
+        message_loop = android::LauncherThread::GetLauncherMessageLoop();

[agrieve, 2017/03/28 19:59:32]

nit: might be nicer to drop the double "Launcher":
android::LauncherThread::GetMessageLoop()

[boliu, 2017/03/28 23:30:52]

Done.

+#endif
         if (redirect_nonUInonIO_browser_threads) {
           non_ui_non_io_task_runner_traits
               .WithPriority(base::TaskPriority::USER_BLOCKING)
@@ -1142,7 +1148,9 @@ int BrowserMainLoop::CreateThreads() {
     BrowserThread::ID id = static_cast<BrowserThread::ID>(thread_id);
 
     if (thread_to_start) {
-      (*thread_to_start).reset(new BrowserProcessSubThread(id));
+      (*thread_to_start)
+          .reset(message_loop ? new BrowserProcessSubThread(id, message_loop)
+                              : new BrowserProcessSubThread(id));
       if (!(*thread_to_start)->StartWithOptions(options))
         LOG(FATAL) << "Failed to start the browser thread: id == " << id;
     } else {