Add SkDEBUGFAIL to clean up use of SkASSERT(!"text");
catch a couple of latent SkASSERT("text") bugs.

http://codereview.appspot.com/5504090/



git-svn-id: http://skia.googlecode.com/svn/trunk@2926 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/core/SkFloat.cpp b/src/core/SkFloat.cpp
index b39e7b9..ffa5d9a 100644
--- a/src/core/SkFloat.cpp
+++ b/src/core/SkFloat.cpp
@@ -216,7 +216,7 @@
 {
     if (packed < 0)
     {
-        SkASSERT(!"can't sqrt a negative number");
+        SkDEBUGFAIL("can't sqrt a negative number");
         return 0;
     }