Revert of PPAPI: Never re-enter JavaScript for PostMessage.

content/renderer/pepper/pepper_hung_plugin_filter.h

Index: content/renderer/pepper/pepper_hung_plugin_filter.h
diff --git a/content/renderer/pepper/pepper_hung_plugin_filter.h b/content/renderer/pepper/pepper_hung_plugin_filter.h
index bc5d3863d3d0ff86720618346b31cb6de617adc5..e7457fd11320800fbbc17033c11e0273efa3a1a6 100644
--- a/content/renderer/pepper/pepper_hung_plugin_filter.h
+++ b/content/renderer/pepper/pepper_hung_plugin_filter.h
@@ -26,10 +26,9 @@
 // thread. This is important since when we're blocked on a sync message to a
 // hung plugin, the main thread is frozen.
 //
-// NOTE: This class is refcounted (via IPC::MessageFilter).
+// NOTE: This class is refcounted (via SyncMessageStatusReceiver).
 class PepperHungPluginFilter
-    : public ppapi::proxy::HostDispatcher::SyncMessageStatusObserver,
-      public IPC::MessageFilter {
+    : public ppapi::proxy::HostDispatcher::SyncMessageStatusReceiver {
  public:
   // The |frame_routing_id| is the ID of the render_frame so that this class can
   // send messages to the browser via that frame's route. The |plugin_child_id|