Make SkImageFilter methods const.

src/core/SkBitmapDevice.cpp

 /*
  * Copyright 2013 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 "SkConfig8888.h"
 #include "SkDraw.h"
@@ skipping 77 matching lines @@
 }
 
 void SkBitmapDevice::clear(SkColor color) {
     fBitmap.eraseColor(color);
 }
 
 const SkBitmap& SkBitmapDevice::onAccessBitmap() {
     return fBitmap;
 }
 
-bool SkBitmapDevice::canHandleImageFilter(SkImageFilter*) {
+bool SkBitmapDevice::canHandleImageFilter(const SkImageFilter*) {
     return false;
 }
 
-bool SkBitmapDevice::filterImage(SkImageFilter* filter, const SkBitmap& src,
+bool SkBitmapDevice::filterImage(const SkImageFilter* filter, const SkBitmap& src,
                                  const SkMatrix& ctm, SkBitmap* result,
                                  SkIPoint* offset) {
     return false;
 }
 
-bool SkBitmapDevice::allowImageFilter(SkImageFilter*) {
+bool SkBitmapDevice::allowImageFilter(const SkImageFilter*) {
     return true;
 }
 
 bool SkBitmapDevice::onReadPixels(const SkBitmap& bitmap,
                                   int x, int y,
                                   SkCanvas::Config8888 config8888) {
     SkASSERT(SkBitmap::kARGB_8888_Config == bitmap.config());
     SkASSERT(!bitmap.isNull());
     SkASSERT(SkIRect::MakeWH(this->width(), this->height()).contains(SkIRect::MakeXYWH(x, y,
                                                                           bitmap.width(),
@@ skipping 282 matching lines @@
         paint.getStyle() != SkPaint::kFill_Style ||
         !SkXfermode::IsMode(paint.getXfermode(), SkXfermode::kSrcOver_Mode)) {
         // turn off lcd
         flags->fFlags = paint.getFlags() & ~SkPaint::kLCDRenderText_Flag;
         flags->fHinting = paint.getHinting();
         return true;
     }
     // we're cool with the paint as is
     return false;
 }