Experiment: add flag for finish-recording to return null

src/core/SkRecordOpts.cpp

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkRecordOpts.h"
 
 #include "SkRecordPattern.h"
@@ skipping 258 matching lines @@
     apply(&pass, record);
 }
 
 ///////////////////////////////////////////////////////////////////////////////////////////////////
 
 void SkRecordOptimize(SkRecord* record) {
     // This might be useful  as a first pass in the future if we want to weed
     // 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);
 
     record->defrag();
 }
 
 void SkRecordOptimize2(SkRecord* record) {
     multiple_set_matrices(record);
     SkRecordNoopSaveRestores(record);
     SkRecordNoopSaveLayerDrawRestores(record);
     SkRecordMergeSvgOpacityAndFilterLayers(record);
 
     record->defrag();
 }