Add GL_CHROMIUM_screen_space_antialiasing to support alternative AA

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 c9edcdd4ff31dc7e7c7c11b41cf96b93089e7fa5..0a4079f7297695412dbb6ae195f5453f16d0d060 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -1060,6 +1060,7 @@ class GLES2DecoderImpl : public GLES2Decoder,
   void DoConsumeTextureCHROMIUM(GLenum target, const GLbyte* key);
   void DoCreateAndConsumeTextureCHROMIUM(GLenum target, const GLbyte* key,
     GLuint client_id);
+  void DoApplyScreenSpaceAntialiasingCHROMIUM();
 
   bool DoIsValuebufferCHROMIUM(GLuint client_id);
   void DoBindValueBufferCHROMIUM(GLenum target, GLuint valuebuffer);
@@ -13847,6 +13848,13 @@ void GLES2DecoderImpl::DoCreateAndConsumeTextureCHROMIUM(GLenum target,
   texture_ref = texture_manager()->Consume(client_id, texture);
 }
 
+void GLES2DecoderImpl::DoApplyScreenSpaceAntialiasingCHROMIUM() {
+  // Apply CMAA(Conservative Morphological Anti-Aliasing) algorithm to the
+  // color attachments of currently bound draw framebuffer.
+  // Reference GL_INTEL_framebuffer_CMAA for details.
+  glApplyFramebufferAttachmentCMAAINTEL();
+}
+
 bool GLES2DecoderImpl::DoIsValuebufferCHROMIUM(GLuint client_id) {
   const Valuebuffer* valuebuffer = GetValuebuffer(client_id);
   return valuebuffer && valuebuffer->IsValid();