Stop using nested message loop for alert() and other JS dialogs

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index 7a5a438053267852f63b2d2a972d5208805c0668..3d8277d842a81c3db63f2154ef38c972ad329ae9 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -2129,7 +2129,7 @@ void RenderFrameImpl::OnTextSurroundingSelectionRequest(uint32_t max_length) {
       surroundingText.endOffsetInTextContent()));
 }
 
-bool RenderFrameImpl::SendAndRunNestedMessageLoop(IPC::SyncMessage* message) {
+bool RenderFrameImpl::SendSyncMessage(IPC::SyncMessage* message) {
   // Before Blink asks us to show an alert (etc.), it takes care of doing the
   // equivalent of WebView::willEnterModalLoop.  In this case it is particularly

[aelias_OOO_until_Jul13, 2016/04/29 05:50:38]

Could you track down what this "equivalent" is and delete it?

[Changwan Ryu, 2016/04/29 08:44:13]

Currently, FlashMessageLoop and PrintWebViewHelper will still call
willEnterModalLoop() to pause resource dispatching until their sync messages get
replied. I'm not sure about the impact of removing the logic in those cases.

   // important that we do not call willEnterModalLoop as that would defer
@@ -2137,7 +2137,6 @@ bool RenderFrameImpl::SendAndRunNestedMessageLoop(IPC::SyncMessage* message) {
   if (RenderThreadImpl::current())  // Will be NULL during unit tests.
     RenderThreadImpl::current()->DoNotNotifyWebKitOfModalLoop();

[aelias_OOO_until_Jul13, 2016/04/29 05:50:38]

This is now unneeded, and there is some more code you can delete as part of this
patch if you follow down this thread.  Please delete both
RenderFrameImpl::SendSyncMessage and RenderThreadImpl::Send() entirely (without
the nested message loop, it looks correct to simply call ChildThreadImpl::Send)
as well as RenderThreadImpl::notify_webkit_of_modal_loop_.

[Changwan Ryu, 2016/04/29 08:44:13]

Removed notify_webkit_of_modal_loop and related function.
RenderFrameImpl::Send() has a logic to check for a detaching message,
so I left it as is.

 
-  message->EnableMessagePumping();  // Runs a nested message loop.
   return Send(message);
 }
 
@@ -2156,7 +2155,7 @@ bool RenderFrameImpl::RunJavaScriptMessage(JavaScriptMessageType type,
   if (!result)
     result = &result_temp;
 
-  SendAndRunNestedMessageLoop(new FrameHostMsg_RunJavaScriptMessage(
+  SendSyncMessage(new FrameHostMsg_RunJavaScriptMessage(
       routing_id_, message, default_value, frame_url, type, &success, result));
   return success;
 }
@@ -3635,7 +3634,7 @@ bool RenderFrameImpl::runModalBeforeUnloadDialog(bool is_reload) {
   // This is an ignored return value, but is included so we can accept the same
   // response as RunJavaScriptMessage.
   base::string16 ignored_result;
-  SendAndRunNestedMessageLoop(new FrameHostMsg_RunBeforeUnloadConfirm(
+  SendSyncMessage(new FrameHostMsg_RunBeforeUnloadConfirm(
       routing_id_, frame_->document().url(), is_reload, &success,
       &ignored_result));
   return success;