Correct DisplayItemList::ApproximateOpCount() for flattened picture

cc/playback/display_item_list.cc

Index: cc/playback/display_item_list.cc
diff --git a/cc/playback/display_item_list.cc b/cc/playback/display_item_list.cc
index 38bd1eb29056ff7dee349876383896a2d0267dfd..f1160531a0f5b775ed640f5b846c9aa2a23ee771 100644
--- a/cc/playback/display_item_list.cc
+++ b/cc/playback/display_item_list.cc
@@ -167,6 +167,7 @@ bool DisplayItemList::RetainsIndividualDisplayItems() const {
 }
 
 void DisplayItemList::Finalize() {
+  TRACE_EVENT0("cc", "DisplayItemList::Finalize");
   // TODO(dtrainor): Need to deal with serializing visual_rects_.
   // http://crbug.com/568757.
   DCHECK(!retain_individual_display_items_ ||
@@ -200,7 +201,9 @@ bool DisplayItemList::IsSuitableForGpuRasterization() const {
 }
 
 int DisplayItemList::ApproximateOpCount() const {
-  return approximate_op_count_;
+  if (retain_individual_display_items_)
+    return approximate_op_count_;
+  return picture_ ? picture_->approximateOpCount() : 0;
 }
 
 size_t DisplayItemList::ApproximateMemoryUsage() const {