DidBeginTracing  1149 cc/layers/layer_impl.cc void LayerImpl::DidBeginTracing() {}
DidBeginTracing   401 cc/layers/picture_layer_impl.cc void PictureLayerImpl::DidBeginTracing() {
DidBeginTracing   438 cc/resources/picture_pile_impl.cc void PicturePileImpl::DidBeginTracing() {