content gpu refactor: get rid of gpu related content switches.

gpu/command_buffer/service/gpu_preferences.h

Index: gpu/command_buffer/service/gpu_preferences.h
diff --git a/gpu/command_buffer/service/gpu_preferences.h b/gpu/command_buffer/service/gpu_preferences.h
index 2721e272aab36002e4a51cefb66082097465f672..52bac066f74e075920e4a8731fe81ac80764ed92 100644
--- a/gpu/command_buffer/service/gpu_preferences.h
+++ b/gpu/command_buffer/service/gpu_preferences.h
@@ -32,6 +32,24 @@ struct GPU_EXPORT GpuPreferences {
   // Prioritizes the UI's command stream in the GPU process.
   bool ui_prioritize_in_gpu_process = false;
 
+  // Disables hardware acceleration of video decode, where available.
+  bool disable_accelerated_video_decode = false;
+
+#if defined(OS_CHROMEOS)
+  // Disables VA-API accelerated video encode.
+  bool disable_vaapi_accelerated_video_encode = false;
+#endif
+
+#if defined(ENABLE_WEBRTC)
+  // Disables HW decode acceleration for WebRTC.

[mcasas, 2016/03/11 20:53:28]

nit: s/decode/encode/

[Peng, 2016/03/11 22:43:16]

Done.

+  bool disable_web_rtc_hw_encoding = false;
+#endif
+
+#if defined(OS_WIN)
+  // Enables experimental hardware acceleration for VP8/VP9 video decoding.
+  bool enable_accelerated_vpx_decode = false;

[mcasas, 2016/03/11 20:53:28]

How would this square with l.36 
|disable_accelerated_video_decode| ?

My feeling is that the ToT usage of the equivalent
of this flag was deliberately kept generic for some
unknown reason ("...just in case...") while being 
used in just one case, i.e. DXVAVideoDecodeAccelerator. 

I suggest this is is a good moment to correct that 
wrong and make this explicit,e.g.
s/enable_accelerated_vpx_decode/enable_dxva_accelerated_video_decode/

[Peng, 2016/03/11 22:43:16]

I think it is better to unify those fields in a separate CL. I will file an
issue for it.

+#endif
+
   // ===================================
   // Settings from //gpu/command_buffer/service/gpu_switches.cc