Correct DisplayItemList::ApproximateOpCount() for flattened picture

cc/playback/recording_source.cc

Index: cc/playback/recording_source.cc
diff --git a/cc/playback/recording_source.cc b/cc/playback/recording_source.cc
index a98a60ed75c9ef61ef34201f2de905efcdf31a80..feaae8807570e375de7348471d7fa2999721a920 100644
--- a/cc/playback/recording_source.cc
+++ b/cc/playback/recording_source.cc
@@ -104,6 +104,7 @@ void RecordingSource::UpdateInvalidationForNewViewport(
 }
 
 void RecordingSource::FinishDisplayItemListUpdate() {
+  TRACE_EVENT0("cc", "RecordingSource::FinishDisplayItemListUpdate");
   DetermineIfSolidColor();
   display_list_->EmitTraceSnapshot();
   if (generate_discardable_images_metadata_)
@@ -227,6 +228,8 @@ void RecordingSource::DetermineIfSolidColor() {
   if (!display_list_->ShouldBeAnalyzedForSolidColor())
     return;
 
+  TRACE_EVENT1("cc", "RecordingSource::DetermineIfSolidColor", "opcount",
+               display_list_->ApproximateOpCount());
   gfx::Size layer_size = GetSize();
   skia::AnalysisCanvas canvas(layer_size.width(), layer_size.height());
   display_list_->Raster(&canvas, nullptr, gfx::Rect(), 1.f);