Create new target to hold gpu test code, enable direct testing of GrEffects in GM.

R=robertphillips@google.com, jvanverth@google.com, egdaniel@google.com

Author: bsalomon@google.com

Review URL: https://chromiumcodereview.appspot.com/23352003

git-svn-id: http://skia.googlecode.com/svn/trunk@10866 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/gm.h b/gm/gm.h
index dbd7f42..b19bce3 100644
--- a/gm/gm.h
+++ b/gm/gm.h
@@ -43,6 +43,8 @@
             kSkipScaledReplay_Flag      = 1 << 6,
             kSkipGPU_Flag               = 1 << 7,
             kSkipPDFRasterization_Flag  = 1 << 8,
+
+            kGPUOnly_Flag               = 1 << 9,
         };
 
         void draw(SkCanvas*);