Make SkImageFilter methods const.

include/pdf/SkPDFDevice.h

 
 /*
  * Copyright 2011 Google Inc.
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 
 #ifndef SkPDFDevice_DEFINED
@@ skipping 195 matching lines @@
      *              to printer.
      */
     void setRasterDpi(SkScalar rasterDpi) {
         fRasterDpi = rasterDpi;
     }
 
 protected:
     virtual bool onReadPixels(const SkBitmap& bitmap, int x, int y,
                               SkCanvas::Config8888) SK_OVERRIDE;
 
-    virtual bool allowImageFilter(SkImageFilter*) SK_OVERRIDE;
+    virtual bool allowImageFilter(const SkImageFilter*) SK_OVERRIDE;
 
 private:
     // TODO(vandebo): push most of SkPDFDevice's state into a core object in
     // order to get the right access levels without using friend.
     friend class ScopedContentEntry;
 
     SkISize fPageSize;
     SkISize fContentSize;
     SkMatrix fInitialTransform;
     SkClipStack fExistingClipStack;
@@ skipping 106 matching lines @@
 
     typedef SkBitmapDevice INHERITED;
 
     // TODO(edisonn): Only SkDocument_PDF and SkPDFImageShader should be able to create
     // an SkPDFDevice
     //friend class SkDocument_PDF;
     //friend class SkPDFImageShader;
 };
 
 #endif