Make SkImageFilter methods const.

src/core/SkImageFilter.cpp

 /*
  * Copyright 2012 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #include "SkImageFilter.h"
 
 #include "SkBitmap.h"
@@ skipping 76 matching lines @@
         if (input != NULL) {
             buffer.writeFlattenable(input);
         }
     }
     buffer.writeRect(fCropRect.rect());
     buffer.writeUInt(fCropRect.flags());
 }
 
 bool SkImageFilter::filterImage(Proxy* proxy, const SkBitmap& src,
                                 const SkMatrix& ctm,
-                                SkBitmap* result, SkIPoint* offset) {
+                                SkBitmap* result, SkIPoint* offset) const {
     SkASSERT(result);
     SkASSERT(offset);
     /*
      *  Give the proxy first shot at the filter. If it returns false, ask
      *  the filter to do it.
      */
     return (proxy && proxy->filterImage(this, src, ctm, result, offset)) ||
            this->onFilterImage(proxy, src, ctm, result, offset);
 }
 
@@ skipping 20 matching lines @@
             SkRect bounds;
             input->computeFastBounds(src, &bounds);
             dst->join(bounds);
         } else {
             dst->join(src);
         }
     }
 }
 
 bool SkImageFilter::onFilterImage(Proxy*, const SkBitmap&, const SkMatrix&,
-                                  SkBitmap*, SkIPoint*) {
+                                  SkBitmap*, SkIPoint*) const {
     return false;
 }
 
 bool SkImageFilter::canFilterImageGPU() const {
     return this->asNewEffect(NULL, NULL, SkMatrix::I(), SkIRect());
 }
 
 bool SkImageFilter::filterImageGPU(Proxy* proxy, const SkBitmap& src, const SkMatrix& ctm,
-                                   SkBitmap* result, SkIPoint* offset) {
+                                   SkBitmap* result, SkIPoint* offset) const {
 #if SK_SUPPORT_GPU
     SkBitmap input;
     SkASSERT(fInputCount == 1);
     SkIPoint srcOffset = SkIPoint::Make(0, 0);
     if (!SkImageFilterUtils::GetInputResultGPU(this->getInput(0), proxy, src, ctm, &input, &srcOffset)) {
         return false;
     }
     GrTexture* srcTexture = input.getTexture();
     SkIRect bounds;
     src.getBounds(&bounds);
@@ skipping 77 matching lines @@
     return true;
 }
 
 bool SkImageFilter::asNewEffect(GrEffectRef**, GrTexture*, const SkMatrix&, const SkIRect&) const {
     return false;
 }
 
 bool SkImageFilter::asColorFilter(SkColorFilter**) const {
     return false;
 }