Shutdown renderer main message loop before blink::shutdown()

content/renderer/render_thread_impl.cc

Index: content/renderer/render_thread_impl.cc
diff --git a/content/renderer/render_thread_impl.cc b/content/renderer/render_thread_impl.cc
index 083099e583465e1ad2aa319e745c23b8ca161eae..69c2050a3f5b8076ab57ce5f971a38302759be76 100644
--- a/content/renderer/render_thread_impl.cc
+++ b/content/renderer/render_thread_impl.cc
@@ -977,6 +977,7 @@ void RenderThreadImpl::Shutdown() {
   renderer_scheduler_->Shutdown();
   if (main_message_loop_)
     base::RunLoop().RunUntilIdle();
+  main_message_loop_ = nullptr;
 
   if (blink_platform_impl_) {
     blink_platform_impl_->Shutdown();
@@ -991,11 +992,6 @@ void RenderThreadImpl::Shutdown() {
   // may try to unlock their underlying discardable memory.
   ChildThreadImpl::ShutdownDiscardableSharedMemoryManager();
 
-  // The message loop must be cleared after shutting down
-  // the DiscardableSharedMemoryManager, which needs to send messages
-  // to the browser process.

[esprehn, 2016/07/19 16:42:54]

You're doing the opposite of what the comment says we have to do now, why is
that correct? You now destroy the message loop before the discardable memory
manager shuts down which means the IPCs won't make it out.

[tzik, 2016/07/19 17:26:52]

The comment looks inaccurate to me.
ChildDiscardableSharedMemoryManager spins the message loop only for a sync IPC
for allocation, and doesn't use it for shutdown.
Though it uses the main thread task runner to check if the current thread is the
main thread, the message loop itself is not needed for it.

-  main_message_loop_.reset();
-
   lazy_tls.Pointer()->Set(nullptr);
 }