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 82e9052c63b7cc621771c35f4c0442676194ed3a..4c48415069cbf7d324e6bd4a2bdb86db1537a820 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -1092,6 +1092,7 @@ class GLES2DecoderImpl : public GLES2Decoder,
   void DoConsumeTextureCHROMIUM(GLenum target, const GLbyte* key);
   void DoCreateAndConsumeTextureCHROMIUM(GLenum target, const GLbyte* key,
     GLuint client_id);
+  void DoApplyScreenSpaceAntialiasing();
 
   bool DoIsValuebufferCHROMIUM(GLuint client_id);
   void DoBindValueBufferCHROMIUM(GLenum target, GLuint valuebuffer);
@@ -13463,6 +13464,13 @@ void GLES2DecoderImpl::DoCreateAndConsumeTextureCHROMIUM(GLenum target,
   texture_ref = texture_manager()->Consume(client_id, texture);
 }
 
+void GLES2DecoderImpl::DoApplyScreenSpaceAntialiasing() {
+    // 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();