This adds a hang monitor for Pepper plugins. It monitors sync messages on the I/O thread of the renderer and sends a message to the browser if it's blocked for too long.

The browser will show an infobar allowing you to terminate the plugin.

BUG=122795

Review URL: https://chromiumcodereview.appspot.com/10014013

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@132245 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/ppapi/proxy/dispatcher.cc b/ppapi/proxy/dispatcher.cc
index a2a1d71..39b1a06 100644
--- a/ppapi/proxy/dispatcher.cc
+++ b/ppapi/proxy/dispatcher.cc
@@ -50,6 +50,9 @@
 
 void Dispatcher::AddIOThreadMessageFilter(
     IPC::ChannelProxy::MessageFilter* filter) {
+  // Our filter is refcounted. The channel will call the destruct method on the
+  // filter when the channel is done with it, so the corresponding Release()
+  // happens there.
   channel()->AddFilter(filter);
 }