Update from https://crrev.com/316786

cc/resources/picture_layer_tiling_set.cc

Index: cc/resources/picture_layer_tiling_set.cc
diff --git a/cc/resources/picture_layer_tiling_set.cc b/cc/resources/picture_layer_tiling_set.cc
index 7c36a3ff552e40ccf701abdb466e489560500562..d9315434860bbd516a8e0b415ca569b50c7667f6 100644
--- a/cc/resources/picture_layer_tiling_set.cc
+++ b/cc/resources/picture_layer_tiling_set.cc
@@ -65,6 +65,13 @@ void PictureLayerTilingSet::UpdateTilingsToCurrentRasterSource(
   // Copy over tilings that are shared with the |twin_set| tiling set (if it
   // exists).
   if (twin_set) {
+    if (twin_set->tilings_.empty()) {
+      // If the twin (pending) tiling set is empty, it was not updated for the
+      // current frame. So we drop tilings from our set as well, instead of
+      // leaving behind unshared tilings that are all non-ideal.
+      RemoveAllTilings();
+    }
+
     for (PictureLayerTiling* twin_tiling : twin_set->tilings_) {
       float contents_scale = twin_tiling->contents_scale();
       DCHECK_GE(contents_scale, minimum_contents_scale);
@@ -479,7 +486,8 @@ PictureLayerTilingSet::CoverageIterator::operator bool() const {
       region_iter_.has_rect();
 }
 
-void PictureLayerTilingSet::AsValueInto(base::debug::TracedValue* state) const {
+void PictureLayerTilingSet::AsValueInto(
+    base::trace_event::TracedValue* state) const {
   for (size_t i = 0; i < tilings_.size(); ++i) {
     state->BeginDictionary();
     tilings_[i]->AsValueInto(state);