Add GL_CHROMIUM_screen_space_antialiasing to support alternative AA

gpu/command_buffer/service/feature_info.h

 // Copyright (c) 2012 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_SERVICE_FEATURE_INFO_H_
 #define GPU_COMMAND_BUFFER_SERVICE_FEATURE_INFO_H_
 
 #include <string>
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
@@ skipping 24 matching lines @@
     bool chromium_color_buffer_float_rgb;
     bool chromium_framebuffer_multisample;
     bool chromium_sync_query;
     // Use glBlitFramebuffer() and glRenderbufferStorageMultisample() with
     // GL_EXT_framebuffer_multisample-style semantics, since they are exposed
     // as core GL functions on this implementation.
     bool use_core_framebuffer_multisample;
     bool multisampled_render_to_texture;
     // Use the IMG GLenum values and functions rather than EXT.
     bool use_img_for_multisampled_render_to_texture;
+    bool chromium_screen_space_antialiasing;
     bool oes_standard_derivatives;
     bool oes_egl_image_external;
     bool oes_depth24;
     bool oes_compressed_etc1_rgb8_texture;
     bool packed_depth24_stencil8;
     bool npot_ok;
     bool enable_texture_float_linear;
     bool enable_texture_half_float_linear;
     bool angle_translated_shader_source;
     bool angle_pack_reverse_row_order;
@@ skipping 121 matching lines @@
   bool disable_shader_translator_;
   scoped_ptr<gfx::GLVersionInfo> gl_version_info_;
 
   DISALLOW_COPY_AND_ASSIGN(FeatureInfo);
 };
 
 }  // namespace gles2
 }  // namespace gpu
 
 #endif  // GPU_COMMAND_BUFFER_SERVICE_FEATURE_INFO_H_