Add support for all blendmodes if we have GL_KHR_blend_equation_advanced.

cc/output/gl_renderer.h

Index: cc/output/gl_renderer.h
diff --git a/cc/output/gl_renderer.h b/cc/output/gl_renderer.h
index 8e53d7023ee1a67d5df589f3dbcec0643178e5f3..bf44d5893e7717f5a51092e63f8182a7d543c534 100644
--- a/cc/output/gl_renderer.h
+++ b/cc/output/gl_renderer.h
@@ -440,6 +440,8 @@ class CC_EXPORT GLRenderer : public DirectRenderer {
   scoped_ptr<SyncQuery> current_sync_query_;
   bool use_sync_query_;
   bool use_blend_minmax_;
+  bool use_blend_equation_advanced_;
+  bool use_blend_equation_advanced_coherent_;
 
   SkBitmap on_demand_tile_raster_bitmap_;
   ResourceProvider::ResourceId on_demand_tile_raster_resource_id_;