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

R=reed@google.com

Author: bsalomon@google.com

Review URL: https://codereview.chromium.org/151843002

git-svn-id: http://skia.googlecode.com/svn/trunk@13279 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/convexpolyclip.cpp b/gm/convexpolyclip.cpp
index db357bb..18b99a7 100644
--- a/gm/convexpolyclip.cpp
+++ b/gm/convexpolyclip.cpp
@@ -182,6 +182,10 @@
         }
     }
 
+    virtual uint32_t onGetFlags() const {
+        return kAsBench_Flag;
+    }
+
 private:
     SkTLList<SkPath> fPaths;
     SkBitmap         fBmp;