cc : Track ids for which active opacity always wins on property trees

cc/layers/painted_scrollbar_layer.cc

Index: cc/layers/painted_scrollbar_layer.cc
diff --git a/cc/layers/painted_scrollbar_layer.cc b/cc/layers/painted_scrollbar_layer.cc
index 98d0b26039a4910fc83b1fb7db4b8c0d67e61836..6bbcf107bb580bdc402cf2bbfd1e3328a72c7552 100644
--- a/cc/layers/painted_scrollbar_layer.cc
+++ b/cc/layers/painted_scrollbar_layer.cc
@@ -70,6 +70,10 @@ bool PaintedScrollbarLayer::OpacityCanAnimateOnImplThread() const {
   return scrollbar_->IsOverlay();
 }
 
+bool PaintedScrollbarLayer::AlwaysUseActiveTreeOpacity() const {
+  return true;
+}
+
 ScrollbarOrientation PaintedScrollbarLayer::orientation() const {
   return scrollbar_->Orientation();
 }