Use a shared thread for media operations.

content/public/test/layouttest_support.h

Index: content/public/test/layouttest_support.h
diff --git a/content/public/test/layouttest_support.h b/content/public/test/layouttest_support.h
index d80123d3a28ab52eab1cc5b650f7d583d09c4314..c8b4761ba8d41ff299f9b77272575415ba68869f 100644
--- a/content/public/test/layouttest_support.h
+++ b/content/public/test/layouttest_support.h
@@ -6,6 +6,7 @@
 #define CONTENT_PUBLIC_TEST_LAYOUTTEST_SUPPORT_H_
 
 #include "base/callback_forward.h"
+#include "base/memory/ref_counted.h"
 
 namespace WebKit {
 class WebGamepads;
@@ -16,6 +17,10 @@ namespace WebTestRunner {
 class WebTestProxyBase;
 }
 
+namespace base {
+class MessageLoopProxy;
+}
+
 namespace content {
 
 class RenderView;
@@ -72,6 +77,12 @@ void DisableSystemDragDrop();
 // Don't show modal popup menus.
 void DisableModalPopupMenus();
 
+// Return the thread on which media operations should run.
+//
+// TODO(scherkus): We should be using RenderViewImpl::createMediaPlayer(), see
+// http://crbug.com/239826
+scoped_refptr<base::MessageLoopProxy> GetMediaThreadMessageLoopProxy();
+
 }  // namespace content
 
 #endif  // CONTENT_PUBLIC_TEST_LAYOUTTEST_SUPPORT_H_