Make SkImageFilter methods const.

src/utils/SkPictureUtils.cpp

 /*
  * Copyright 2012 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkBitmapDevice.h"
 #include "SkCanvas.h"
 #include "SkData.h"
@@ skipping 57 matching lines @@
     virtual GrRenderTarget* accessRenderTarget() SK_OVERRIDE { return NULL; }
     virtual bool filterTextFlags(const SkPaint& paint, TextFlags*) SK_OVERRIDE {
         return false;
     }
     // TODO: allow this call to return failure, or move to SkBitmapDevice only.
     virtual const SkBitmap& onAccessBitmap() SK_OVERRIDE {
         return fEmptyBitmap;
     }
     virtual void lockPixels() SK_OVERRIDE { nothing_to_do(); }
     virtual void unlockPixels() SK_OVERRIDE { nothing_to_do(); }
-    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;
     }
 
     virtual void clear(SkColor color) SK_OVERRIDE {
         nothing_to_do();
     }
     virtual void writePixels(const SkBitmap& bitmap, int x, int y,
                              SkCanvas::Config8888 config8888) SK_OVERRIDE {
         not_supported();
@@ skipping 138 matching lines @@
     canvas.clipRect(area, SkRegion::kIntersect_Op, false);
     canvas.drawPicture(*pict);
 
     SkData* data = NULL;
     int count = array.count();
     if (count > 0) {
         data = SkData::NewFromMalloc(array.detach(), count * sizeof(SkPixelRef*));
     }
     return data;
 }