Move a bunch of content\common code into the content namespace.

content/common/gpu/media/dxva_video_decode_accelerator.h

Index: content/common/gpu/media/dxva_video_decode_accelerator.h
===================================================================
--- content/common/gpu/media/dxva_video_decode_accelerator.h	(revision 163460)
+++ content/common/gpu/media/dxva_video_decode_accelerator.h	(working copy)
@@ -22,6 +22,8 @@
 interface IMFSample;
 interface IDirect3DSurface9;
 
+namespace content {
+
 // Class to provide a DXVA 2.0 based accelerator using the Microsoft Media
 // foundation APIs via the VideoDecodeAccelerator interface.
 // This class lives on a single thread and DCHECKs that it is never accessed
@@ -217,4 +219,6 @@
   base::Callback<bool(void)> make_context_current_;
 };
 
+}  // namespace content
+
 #endif  // CONTENT_COMMON_GPU_MEDIA_DXVA_VIDEO_DECODE_ACCELERATOR_H_