Don't enable CHROMIUM_ycbcr_420v_image when using mesa.

gpu/command_buffer/service/feature_info.cc

Index: gpu/command_buffer/service/feature_info.cc
diff --git a/gpu/command_buffer/service/feature_info.cc b/gpu/command_buffer/service/feature_info.cc
index d8edc1f7f5a5063d94bfea3c2650f8d3cd7cb58d..0223abaa120d777389403bbb5df041056881c4f3 100644
--- a/gpu/command_buffer/service/feature_info.cc
+++ b/gpu/command_buffer/service/feature_info.cc
@@ -1004,8 +1004,10 @@ void FeatureInfo::InitializeFeatures() {
 
 #if defined(OS_MACOSX)
   AddExtensionString("GL_CHROMIUM_iosurface");
-  AddExtensionString("GL_CHROMIUM_ycbcr_420v_image");
-  feature_flags_.chromium_image_ycbcr_420v = true;
+  if (gfx::GetGLImplementation() != gfx::kGLImplementationOSMesaGL) {

[reveman, 2016/02/10 03:12:14]

should GL_CHROMIUM_iosurface also be moved inside this scope?

[Daniele Castagna, 2016/02/10 03:14:56]

Sure, IIRC you mentioned GL_CHROMIUM_iosurface is not used anymore, if that's
the case we can just clean that up in another CL.
What do you prefer? 

[Daniele Castagna, 2016/02/10 03:41:36]

Moved AddExtensionString("GL_CHROMIUM_iosurface") in the if body.

+    AddExtensionString("GL_CHROMIUM_ycbcr_420v_image");
+    feature_flags_.chromium_image_ycbcr_420v = true;
+  }
 #endif
 
   if (extensions.Contains("GL_APPLE_ycbcr_422")) {