Fix jank during mac resize

content/browser/renderer_host/render_widget_host_impl.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/renderer_host/render_widget_host_impl.h"
 
 #include <math.h>
 
 #include <set>
 #include <tuple>
@@ skipping 423 matching lines @@
   }
 
   Destroy(also_delete);
 }
 
 bool RenderWidgetHostImpl::IsLoading() const {
   return is_loading_;
 }
 
 bool RenderWidgetHostImpl::OnMessageReceived(const IPC::Message &msg) {
-  // Only process messages if the RenderWidget is alive.
-  if (!renderer_initialized())
-    return false;
+  // Only process most messages if the RenderWidget is alive.
+  if (!renderer_initialized()) {
+    // SetNeedsBeginFrame messages are only sent by the renderer once and so
+    // should never be dropped.
+    bool handled = true;
+    IPC_BEGIN_MESSAGE_MAP(RenderWidgetHostImpl, msg)
+      IPC_MESSAGE_HANDLER(ViewHostMsg_SetNeedsBeginFrames,
+                          OnSetNeedsBeginFrames)
+      IPC_MESSAGE_UNHANDLED(handled = false)
+    IPC_END_MESSAGE_MAP()
+    return handled;
+  }
 
   if (owner_delegate_ && owner_delegate_->OnMessageReceived(msg))
     return true;
 
   bool handled = true;
   IPC_BEGIN_MESSAGE_MAP(RenderWidgetHostImpl, msg)
     IPC_MESSAGE_HANDLER(FrameHostMsg_RenderProcessGone, OnRenderProcessGone)
     IPC_MESSAGE_HANDLER(FrameHostMsg_HittestData, OnHittestData)
     IPC_MESSAGE_HANDLER(InputHostMsg_QueueSyntheticGesture,
                         OnQueueSyntheticGesture)
@@ skipping 1732 matching lines @@
   return delegate_ ? delegate_->GetRootBrowserAccessibilityManager() : NULL;
 }
 
 BrowserAccessibilityManager*
     RenderWidgetHostImpl::GetOrCreateRootBrowserAccessibilityManager() {
   return delegate_ ?
       delegate_->GetOrCreateRootBrowserAccessibilityManager() : NULL;
 }
 
 }  // namespace content