Make SkImageFilter methods const.

src/utils/SkGatherPixelRefsAndRects.h

 /*
  * Copyright 2014 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkGatherPixelRefsAndRects_DEFINED
 #define SkGatherPixelRefsAndRects_DEFINED
 
@@ skipping 281 matching lines @@
         return fEmptyBitmap;
     }
     virtual bool onReadPixels(const SkBitmap& bitmap,
                               int x, int y,
                               SkCanvas::Config8888 config8888) SK_OVERRIDE {
         NotSupported();
         return false;
     }
     virtual void lockPixels() SK_OVERRIDE { NothingToDo(); }
     virtual void unlockPixels() SK_OVERRIDE { NothingToDo(); }
-    virtual bool allowImageFilter(SkImageFilter*) SK_OVERRIDE { return false; }
-    virtual bool canHandleImageFilter(SkImageFilter*) SK_OVERRIDE { return false; }
-    virtual bool filterImage(SkImageFilter*, const SkBitmap&, const SkMatrix&,
+    virtual bool allowImageFilter(const SkImageFilter*) SK_OVERRIDE { return false; }
+    virtual bool canHandleImageFilter(const SkImageFilter*) SK_OVERRIDE { return false; }
+    virtual bool filterImage(const SkImageFilter*, const SkBitmap&, const SkMatrix&,
                              SkBitmap* result, SkIPoint* offset) SK_OVERRIDE {
         return false;
     }
 
 private:
     SkPictureUtils::SkPixelRefContainer* fPRCont;
     SkISize                              fSize;
 
     SkBitmap                             fEmptyBitmap; // legacy -- need to remove
 
@@ skipping 25 matching lines @@
     static void NotSupported() {
         SkDEBUGFAIL("this method should never be called");
     }
 
     static void NothingToDo() {}
 
     typedef SkBaseDevice INHERITED;
 };
 
 #endif // SkGatherPixelRefsAndRects_DEFINED