cc: Avoid ResourceProvider nullptr deref

cc/trees/layer_tree_host_impl.h

Index: cc/trees/layer_tree_host_impl.h
diff --git a/cc/trees/layer_tree_host_impl.h b/cc/trees/layer_tree_host_impl.h
index 27f2f504ef57229b1f1ec6348a086df6433b6305..5d6e070b09bac7da83caba20b07541a0ca433077 100644
--- a/cc/trees/layer_tree_host_impl.h
+++ b/cc/trees/layer_tree_host_impl.h
@@ -838,6 +838,10 @@ class CC_EXPORT LayerTreeHostImpl
   bool requires_high_res_to_draw_;
   bool is_likely_to_require_a_draw_;
 
+  // TODO(danakj): Delete the compositor frame sink and all resources when
+  // it's lost instead of having this bool.
+  bool has_valid_compositor_frame_sink_;
+
   std::unique_ptr<Viewport> viewport_;
 
   std::unique_ptr<LayerTreeMutator> mutator_;