Add GL_CHROMIUM_screen_space_antialiasing to support alternative AA

mojo/gpu/mojo_gles2_impl_autogen.h

Index: mojo/gpu/mojo_gles2_impl_autogen.h
diff --git a/mojo/gpu/mojo_gles2_impl_autogen.h b/mojo/gpu/mojo_gles2_impl_autogen.h
index 0d1047b5a5ebef3a7b82ffd7fba0be72926957b3..f5f8b751f2c2e7be10096611b5c0714e9b325e88 100644
--- a/mojo/gpu/mojo_gles2_impl_autogen.h
+++ b/mojo/gpu/mojo_gles2_impl_autogen.h
@@ -815,6 +815,7 @@ class MojoGLES2Impl : public gpu::gles2::GLES2Interface {
                                           GLenum coverMode) override;
   GLenum GetGraphicsResetStatusKHR() override;
   void BlendBarrierKHR() override;
+  void ApplyScreenSpaceAntialiasingCHROMIUM() override;
 
  private:
   MojoGLES2Context context_;