Implement a computeFastBounds() traversal for SkImageFilter. This allows for correct culling of pri…

include/core/SkImageFilter.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 SkImageFilter_DEFINED
 #define SkImageFilter_DEFINED
 
@@ skipping 125 matching lines @@
      *  rect is set at construction time, and determines which pixels from the
      *  input image will be processed. The size of the crop rect should be
      *  used as the size of the destination image. The origin of this rect
      *  should be used to offset access to the input images, and should also
      *  be added to the "offset" parameter in onFilterImage and
      *  filterImageGPU(). (The latter ensures that the resulting buffer is
      *  drawn in the correct location.)
      */
     bool cropRectIsSet() const { return fCropRect.flags() != 0x0; }
 
+    // Default impl returns union of all input bounds.
+    virtual void computeFastBounds(const SkRect&, SkRect*) const;
+
     SK_DEFINE_FLATTENABLE_TYPE(SkImageFilter)
 
 protected:
     SkImageFilter(int inputCount, SkImageFilter** inputs, const CropRect* cropRect = NULL);
 
     // Convenience constructor for 1-input filters.
     explicit SkImageFilter(SkImageFilter* input, const CropRect* cropRect = NULL);
 
     // Convenience constructor for 2-input filters.
     SkImageFilter(SkImageFilter* input1, SkImageFilter* input2, const CropRect* cropRect = NULL);
@@ skipping 58 matching lines @@
                              const SkIRect& bounds) const;
 
 private:
     typedef SkFlattenable INHERITED;
     int fInputCount;
     SkImageFilter** fInputs;
     CropRect fCropRect;
 };
 
 #endif