add flag to skip gpu test



git-svn-id: http://skia.googlecode.com/svn/trunk@8036 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/gm/gmmain.cpp b/gm/gmmain.cpp
index 3f742d9..588ddb9 100644
--- a/gm/gmmain.cpp
+++ b/gm/gmmain.cpp
@@ -1473,6 +1473,10 @@
                 (SkBitmap::kRGB_565_Config == config.fConfig)) {
                 continue;
             }
+            if ((gmFlags & GM::kSkipGPU_Flag) &&
+                kGPU_Backend == config.fBackend) {
+                continue;
+            }
 
             // Now we know that we want to run this test and record its
             // success or failure.