Implement correct clipping for image filters.

src/effects/SkOffsetImageFilter.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 "SkOffsetImageFilter.h"
 #include "SkBitmap.h"
 #include "SkCanvas.h"
@@ skipping 54 matching lines @@
     }
     return true;
 }
 
 void SkOffsetImageFilter::computeFastBounds(const SkRect& src, SkRect* dst) const {
     if (getInput(0)) {
         getInput(0)->computeFastBounds(src, dst);
     } else {
         *dst = src;
     }
+    SkRect copy = *dst;
     dst->offset(fOffset.fX, fOffset.fY);
+    dst->join(copy);
 }
 
 bool SkOffsetImageFilter::onFilterBounds(const SkIRect& src, const SkMatrix& ctm,
-                                         SkIRect* dst) {
+                                         SkIRect* dst) const {
     SkVector vec;
     ctm.mapVectors(&vec, &fOffset, 1);
 
     *dst = src;
-    dst->offset(SkScalarRoundToInt(vec.fX), SkScalarRoundToInt(vec.fY));
+    dst->offset(-SkScalarCeilToInt(vec.fX), -SkScalarCeilToInt(vec.fY));
+    dst->join(src);
     return true;
 }
 
 void SkOffsetImageFilter::flatten(SkWriteBuffer& buffer) const {
     this->INHERITED::flatten(buffer);
     buffer.writePoint(fOffset);
 }
 
 SkOffsetImageFilter::SkOffsetImageFilter(SkScalar dx, SkScalar dy, SkImageFilter* input,
                                          const CropRect* cropRect) : INHERITED(input, cropRect) {
     fOffset.set(dx, dy);
 }
 
 SkOffsetImageFilter::SkOffsetImageFilter(SkReadBuffer& buffer)
   : INHERITED(1, buffer) {
     buffer.readPoint(&fOffset);
     buffer.validate(SkScalarIsFinite(fOffset.fX) &&
                     SkScalarIsFinite(fOffset.fY));
 }