My clang now doesn't complain about !"foo".

BUG=
R=robertphillips@google.com

Review URL: https://codereview.chromium.org/22875037

git-svn-id: http://skia.googlecode.com/svn/trunk@10874 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrAtlas.cpp b/src/gpu/GrAtlas.cpp
index 9184929..9776326 100644
--- a/src/gpu/GrAtlas.cpp
+++ b/src/gpu/GrAtlas.cpp
@@ -189,7 +189,7 @@
         case kA888_GrMaskFormat:
             return kSkia8888_GrPixelConfig;
         default:
-            SkASSERT(!"unknown maskformat");
+            SkDEBUGFAIL("unknown maskformat");
     }
     return kUnknown_GrPixelConfig;
 }