fix mozilla bug

include/gpu/GrClip.h

 /*
  * Copyright 2010 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef GrClip_DEFINED
 #define GrClip_DEFINED
 
@@ skipping 67 matching lines @@
                 if (this->clipStack() && other.clipStack()) {
                     return *this->clipStack() == *other.clipStack();
                 } else {
                     return this->clipStack() == other.clipStack();
                 }
                 break;
             case kIRect_ClipType:
                 return this->irect() == other.irect();
                 break;
         }
+        SkFAIL("This should not occur\n");
+        return false;
     }
 
     bool operator!=(const GrClip& other) const {
         return !(*this == other);
     }
 
     const SkClipStack* clipStack() const {
         SkASSERT(kClipStack_ClipType == fClipType);
         return fClip.fStack;
     }
@@ skipping 76 matching lines @@
     union Clip {
         const SkClipStack* fStack;
         SkIRect fIRect;
     } fClip;
 
     SkIPoint fOrigin;
     ClipType fClipType;
 };
 
 #endif