Experiment: add flag for finish-recording to return null

src/core/SkRecordOpts.cpp

Index: src/core/SkRecordOpts.cpp
diff --git a/src/core/SkRecordOpts.cpp b/src/core/SkRecordOpts.cpp
index ea19d6eaa576e38eeec396464ef43f6799d96b14..aa07facb19752f63f9c3439daa7fda02b892c2f0 100644
--- a/src/core/SkRecordOpts.cpp
+++ b/src/core/SkRecordOpts.cpp
@@ -276,7 +276,7 @@ void SkRecordOptimize(SkRecord* record) {
     // out junk for other optimization passes.  Right now, nothing needs it,
     // and the bounding box hierarchy will do the work of skipping no-op
     // Save-NoDraw-Restore sequences better than we can here.
-    //SkRecordNoopSaveRestores(record);
+    SkRecordNoopSaveRestores(record);
 
     SkRecordNoopSaveLayerDrawRestores(record);
     SkRecordMergeSvgOpacityAndFilterLayers(record);