Add plumbing for two gpu workarounds, soon to be used by DrawingBuffer.

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 d4d0fab085fbfcc7d9713bf5b20bb2eb8a8152c1..890713aa3a1df9aa848d37207e0fb9294027db85 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -3262,6 +3262,11 @@ Capabilities GLES2DecoderImpl::GetCapabilities() {
       feature_info_->feature_flags().occlusion_query_boolean;
   caps.timer_queries =
       query_manager_->GPUTimingAvailable();
+  caps.disable_webgl_multisampling_color_mask_usage =
+      feature_info_->workarounds().disable_webgl_multisampling_color_mask_usage;
+  caps.disable_webgl_rgb_multisampling_usage =
+      feature_info_->workarounds().disable_webgl_rgb_multisampling_usage;
+
   return caps;
 }