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

gpu/command_buffer/common/capabilities.h

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef GPU_COMMAND_BUFFER_COMMON_CAPABILITIES_H_
 #define GPU_COMMAND_BUFFER_COMMON_CAPABILITIES_H_
 
 #include <stdint.h>
 
 #include "gpu/gpu_export.h"
@@ skipping 126 matching lines @@
   bool texture_rg;
   bool texture_half_float_linear;
   bool image_ycbcr_422;
   bool image_ycbcr_420v;
   bool render_buffer_format_bgra8888;
   bool occlusion_query_boolean;
   bool timer_queries;
   bool surfaceless;
   bool flips_vertically;
   bool msaa_is_slow;
+  bool disable_webgl_multisampling_color_mask_usage;
+  bool disable_webgl_rgb_multisampling_usage;
 
   // When this parameter is true, a CHROMIUM image created with RGB format will
   // actually have RGBA format. The client is responsible for handling most of
   // the complexities associated with this. See
   // gpu/GLES2/extensions/CHROMIUM/CHROMIUM_gpu_memory_buffer_image.txt for more
   // details.
   bool chromium_image_rgb_emulation;
 
   int major_version;
   int minor_version;
 };
 
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_COMMON_CAPABILITIES_H_