Revert of content/common: Remove use of MessageLoopProxy and deprecated MessageLoop APIs

content/common/gpu/media/v4l2_video_encode_accelerator.h

Index: content/common/gpu/media/v4l2_video_encode_accelerator.h
diff --git a/content/common/gpu/media/v4l2_video_encode_accelerator.h b/content/common/gpu/media/v4l2_video_encode_accelerator.h
index d292f22f1c9167ad4c1c809da0bb1268759d78cb..165da9dc5cc8fef2c9f6f0366e6ad5a357001d0c 100644
--- a/content/common/gpu/media/v4l2_video_encode_accelerator.h
+++ b/content/common/gpu/media/v4l2_video_encode_accelerator.h
@@ -17,6 +17,12 @@
 #include "content/common/gpu/media/v4l2_image_processor.h"
 #include "media/video/video_encode_accelerator.h"
 #include "ui/gfx/geometry/size.h"
+
+namespace base {
+
+class MessageLoopProxy;
+
+}  // namespace base
 
 namespace media {
 
@@ -186,8 +192,8 @@
   // Set controls in |ctrls| and return true if successful.
   bool SetExtCtrls(std::vector<struct v4l2_ext_control> ctrls);
 
-  // Our original calling task runner for the child thread.
-  const scoped_refptr<base::SingleThreadTaskRunner> child_task_runner_;
+  // Our original calling message loop for the child thread.
+  const scoped_refptr<base::MessageLoopProxy> child_message_loop_proxy_;
 
   gfx::Size visible_size_;
   // Input allocated size required by the device.
@@ -256,7 +262,7 @@
 
   // To expose client callbacks from VideoEncodeAccelerator.
   // NOTE: all calls to these objects *MUST* be executed on
-  // child_task_runner_.
+  // child_message_loop_proxy_.
   base::WeakPtr<Client> client_;
   scoped_ptr<base::WeakPtrFactory<Client> > client_ptr_factory_;