Fixed DCHECK in InProcessGpuThread shutdown.

Upon BrowserMainRunner::Shutdown(), InProcessGpuThread sometimes (race condition)
terminates simply by exiting the message loop due to closed RPC channel, the
ThreadWasQuitProperly flag is required to signal correct termnation in this
case.

BUG=

Review URL: https://codereview.chromium.org/323513003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@275848 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/content/gpu/in_process_gpu_thread.cc b/content/gpu/in_process_gpu_thread.cc
index 59a257d..8a7818d 100644
--- a/content/gpu/in_process_gpu_thread.cc
+++ b/content/gpu/in_process_gpu_thread.cc
@@ -27,6 +27,7 @@
 }
 
 void InProcessGpuThread::CleanUp() {
+  SetThreadWasQuitProperly(true);
   delete gpu_process_;
 }