DXVA: Add --disable-low-latency-dxva to disable low latency decoding

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 1f3a80dc0124767192e4dfd394fed1fa1bab35f6..49e73d662c3e2d99e90a66ca5a2ce90e0d0ae5b6 100644
--- a/gpu/command_buffer/service/gpu_preferences.h
+++ b/gpu/command_buffer/service/gpu_preferences.h
@@ -61,6 +61,9 @@ struct GPU_EXPORT GpuPreferences {
   // Bitmask - 0x1=Microsoft, 0x2=AMD, 0x03=Try all.
   VpxDecodeVendors enable_accelerated_vpx_decode = VPX_VENDOR_MICROSOFT;
 
+  // Enables using CODECAPI_AVLowLatencyMode.
+  bool enable_low_latency_dxva = true;

[piman, 2016/11/07 20:40:14]

You need to add this to content/common/gpu_host_messages.h so that the field
gets correctly transferred over IPC.

[sandersd (OOO until July 31), 2016/11/07 20:43:38]

Done.

+
   // Enables support for avoiding copying DXGI NV12 textures.
   bool enable_zero_copy_dxgi_video = false;