GM is passing the wrong flag to beginRecording() for --rtree.

BUG=
R=epoger@google.com, reed@google.com

Author: mtklein@google.com

Review URL: https://codereview.chromium.org/50713004

git-svn-id: http://skia.googlecode.com/svn/trunk@12011 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/gmmain.cpp b/gm/gmmain.cpp
index 6719d67..92c70b5 100644
--- a/gm/gmmain.cpp
+++ b/gm/gmmain.cpp
@@ -1724,7 +1724,7 @@
             errorsForAllModes.add(kIntentionallySkipped_ErrorType);
         } else {
             SkPicture* pict = gmmain.generate_new_picture(
-                gm, kRTree_BbhType, SkPicture::kUsePathBoundsForClip_RecordingFlag);
+                gm, kRTree_BbhType, SkPicture::kOptimizeForClippedPlayback_RecordingFlag);
             SkAutoUnref aur(pict);
             SkBitmap bitmap;
             gmmain.generate_image_from_picture(gm, compareConfig, pict, &bitmap);