Fix some linux build warnings
Review URL: https://codereview.appspot.com/6571050

git-svn-id: http://skia.googlecode.com/svn/trunk@5675 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/SkGpuDevice.cpp b/src/gpu/SkGpuDevice.cpp
index bcda7d8..4858041 100644
--- a/src/gpu/SkGpuDevice.cpp
+++ b/src/gpu/SkGpuDevice.cpp
@@ -300,6 +300,7 @@
             return kRGBA_8888_GrPixelConfig;
         default:
             GrCrash("Unexpected Config8888.");
+            *flags = 0; // suppress warning
             return kSkia8888_PM_GrPixelConfig;
     }
 }