Update GL_IMPLEMENTATION_COLOR_READ_FORMAT for BGRA

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index a3ad42338965a9e9f7e5c85fb6e133d83079545d..59840bda22d93b94016c39eee56825134ee10e21 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -5114,7 +5114,9 @@ bool GLES2DecoderImpl::GetHelper(
               return true;
           }
           *params = GLES2Util::GetGLReadPixelsImplementationFormat(
-              GetBoundReadFrameBufferInternalFormat());
+              GetBoundReadFrameBufferInternalFormat(),
+              GetBoundReadFrameBufferTextureType(),
+              context_->HasExtension("GL_EXT_read_format_bgra"));

[piman, 2016/03/07 21:04:14]

Actually, here you're only asking the underlying GL context, not what we expose
to the client. That is, you'd pass false on desktop GL, when you'd want to pass
true.

My suggestion is to add a ext_read_format_bgra field in
FeatureInfo::FeatureFlags, that would be set in feature_info.cc where we enable
the extension (similar to, e.g. ext_texture_format_bgra8888) and use that here.

[ericrk, 2016/03/08 00:07:18]

ah, yeah, missed that - thanks! Added this to a feature flag and updated.

         }
         return true;
       case GL_IMPLEMENTATION_COLOR_READ_TYPE: