Allow GMs ato be used as benchmarks. Make convex_poly_clip opt in.

gm/convexpolyclip.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 "gm.h"
 
@@ skipping 164 matching lines @@
                                  0, 1.5f * txtPaint.getTextSize(),
                                  txtPaint);
                 canvas->restore();
                 x += fBmp.width() + kMargin;
             }
 
             y += fBmp.height() + kMargin;
         }
     }
 
+    virtual uint32_t onGetFlags() const {
+        return kAsBench_Flag;
+    }
+
 private:
     SkTLList<SkPath> fPaths;
     SkBitmap         fBmp;
 
     typedef GM INHERITED;
 };
 
 DEF_GM( return SkNEW(ConvexPolyClip); )
 
 }