Call set_unblock(true) on async resize message to guarantee its...

chrome/renderer/command_buffer_proxy.cc

Index: chrome/renderer/command_buffer_proxy.cc
===================================================================
--- chrome/renderer/command_buffer_proxy.cc	(revision 46421)
+++ chrome/renderer/command_buffer_proxy.cc	(working copy)
@@ -184,7 +184,21 @@
 }
 
 void CommandBufferProxy::ResizeOffscreenFrameBuffer(const gfx::Size& size) {
-  Send(new GpuCommandBufferMsg_ResizeOffscreenFrameBuffer(route_id_, size));
+  IPC::Message* message =
+      new GpuCommandBufferMsg_ResizeOffscreenFrameBuffer(route_id_, size);
+  // We need to set the unblock flag on this message to guarantee the
+  // order in which it is processed in the GPU process. Ordinarily in
+  // certain situations, namely if a synchronous message is being
+  // processed, other synchronous messages may be processed before
+  // asynchronous messages. During some page reloads WebGL seems to
+  // send three messages (sync, async, sync) in rapid succession in
+  // that order, and the sync message (GpuCommandBufferMsg_Flush, on
+  // behalf of SwapBuffers) is sometimes processed before the async
+  // message (GpuCommandBufferMsg_ResizeOffscreenFrameBuffer). This
+  // causes the WebGL content to disappear because the back buffer is
+  // not correctly resized.
+  message->set_unblock(true);
+  Send(message);
 }
 
 #if defined(OS_MACOSX)