Experiment: add flag for finish-recording to return null

tests/RecordReplaceDrawTest.cpp

Index: tests/RecordReplaceDrawTest.cpp
diff --git a/tests/RecordReplaceDrawTest.cpp b/tests/RecordReplaceDrawTest.cpp
index 0dd804ec9d024e33c8f86a6d90b22c6e25e5951b..388bee8d7b5dd1efffbe0cefee9aaa1470d27f97 100644
--- a/tests/RecordReplaceDrawTest.cpp
+++ b/tests/RecordReplaceDrawTest.cpp
@@ -78,6 +78,11 @@ DEF_TEST(RecordReplaceDraw_Unbalanced, r) {
         canvas->save();
         canvas->scale(2, 2);
         pic = recorder.finishRecordingAsPicture();
+
+        // we may have optimized everything away. If so, just return
+        if (pic->approximateOpCount() == 0) {
+            return;
+        }
     }
 
     SkRecord rerecord;