fix broken clang build

src/utils/SkCanvasStack.h

 
 /*
  * Copyright 2013 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkCanvasStack_DEFINED
 #define SkCanvasStack_DEFINED
 
 #include "SkNWayCanvas.h"
 #include "SkTArray.h"
 
 class SkCanvasStack : public SkNWayCanvas {
 public:
     SkCanvasStack(int width, int height);
     virtual ~SkCanvasStack();
 
     void pushCanvas(SkCanvas* canvas, const SkIPoint& origin);
     virtual void removeAll() SK_OVERRIDE;
 
     /*
      * The following add/remove canvas methods are overrides from SkNWayCanvas
      * that do not make sense in the context of our CanvasStack, but since we
      * can share most of the other implementation of NWay we override those
      * methods to be no-ops.
      */
-    virtual void addCanvas(SkCanvas*) SK_OVERRIDE { SkASSERT(!"Invalid Op"); }
-    virtual void removeCanvas(SkCanvas*) SK_OVERRIDE { SkASSERT(!"Invalid Op"); }
+    virtual void addCanvas(SkCanvas*) SK_OVERRIDE { SkDEBUGFAIL("Invalid Op"); }
+    virtual void removeCanvas(SkCanvas*) SK_OVERRIDE { SkDEBUGFAIL("Invalid Op"); }
 
     virtual void setMatrix(const SkMatrix& matrix) SK_OVERRIDE;
     virtual bool clipRect(const SkRect&, SkRegion::Op, bool) SK_OVERRIDE;
     virtual bool clipRRect(const SkRRect&, SkRegion::Op, bool) SK_OVERRIDE;
     virtual bool clipPath(const SkPath&, SkRegion::Op, bool) SK_OVERRIDE;
     virtual bool clipRegion(const SkRegion& deviceRgn,
                             SkRegion::Op) SK_OVERRIDE;
 
 private:
     void clipToZOrderedBounds();
 
     struct CanvasData {
         SkIPoint origin;
         SkRegion requiredClip;
     };
 
     SkTArray<CanvasData> fCanvasData;
 
     typedef SkNWayCanvas INHERITED;
 };
 
 #endif