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/bench/benchmain.cpp b/bench/benchmain.cpp
index 9cb7468..c2ba7f3 100644
--- a/bench/benchmain.cpp
+++ b/bench/benchmain.cpp
@@ -223,7 +223,7 @@
 #endif
         case kPDF_Backend:
         default:
-            SkASSERT(!"unsupported");
+            SkDEBUGFAIL("unsupported");
     }
     return device;
 }