Comment 1 for bug 1442413

So, more info:

- The compositor thread isn't doing a sync call that relies on the GPU service - it's handled on the browser side by the IO and FILE_USER_BLOCKING threads.

- The browser process has definitely gone away.

- Despite this, IPC::SyncMessageFilter::OnChannelError() hasn't been called (IPC::SyncMessageFilter::sender_ hasn't been cleared), which would unblock the waiting thread. This should be called on the IO thread from the corresponding IPC::ChannelProxy when the underlying IPC::ChannelMojo is closed.

I suspect this is caused by https://code.google.com/p/chromium/issues/detail?id=377980 (it's enabled by default in 1.7, but not in 1.6). I'm going to disable this on the 1.7 branch just to see.