Mac: Ensure that Mach messages always get a reply

content/child/child_io_surface_manager_mac.cc

Index: content/child/child_io_surface_manager_mac.cc
diff --git a/content/child/child_io_surface_manager_mac.cc b/content/child/child_io_surface_manager_mac.cc
index fb4ef9ac6524992b20166de6be75ca9ccf1f3b0c..b3408463087cde6406e18a4a92a6f3b969d28b76 100644
--- a/content/child/child_io_surface_manager_mac.cc
+++ b/content/child/child_io_surface_manager_mac.cc
@@ -129,6 +129,11 @@ IOSurfaceRef ChildIOSurfaceManager::AcquireIOSurface(
     return nullptr;
   }
 
+  // Crash the renderer (for now) to see if this was the cause of renderer hangs
+  // that have recently been noticed.
+  // http://crbug.com/532149
+  CHECK(data.reply.msg.result);
+
   // Deallocate the right after creating an IOSurface reference.
   base::mac::ScopedMachSendRight scoped_io_surface_right(
       data.reply.msg.io_surface_port.name);