Add cc::SurfaceInfo::is_valid()

cc/trees/layer_tree_host_impl.cc

Index: cc/trees/layer_tree_host_impl.cc
diff --git a/cc/trees/layer_tree_host_impl.cc b/cc/trees/layer_tree_host_impl.cc
index 132616ef303232e01822a4a4dd03ebb7dd1dbb86..18bccfef6f81132a6e7226298f45f66328803e46 100644
--- a/cc/trees/layer_tree_host_impl.cc
+++ b/cc/trees/layer_tree_host_impl.cc
@@ -1602,7 +1602,7 @@ CompositorFrameMetadata LayerTreeHostImpl::MakeCompositorFrameMetadata() const {
         surface_layer_impl->primary_surface_info().id());
     // We need to retain a reference to the fallback surface too so that it's
     // guaranteed to be available when needed.
-    if (surface_layer_impl->fallback_surface_info().id().is_valid()) {
+    if (surface_layer_impl->fallback_surface_info().is_valid()) {
       metadata.referenced_surfaces.push_back(
           surface_layer_impl->fallback_surface_info().id());
     }