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

src/effects/SkBlurImageFilter.cpp

 /*
  * Copyright 2011 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 "SkBitmap.h"
 #include "SkBlurImageFilter.h"
 #include "SkColorPriv.h"
@@ skipping 206 matching lines @@
         boxBlurX(d,  w,  t, kernelSizeX,  highOffsetX, lowOffsetX,  w, h);
         boxBlurX(t,  w,  d, kernelSizeX3, highOffsetX, highOffsetX, w, h);
     } else if (kernelSizeY > 0) {
         boxBlurYX(s, sw, d, kernelSizeY,  lowOffsetY,  highOffsetY, h, w);
         boxBlurX(d,  h,  t, kernelSizeY,  highOffsetY, lowOffsetY,  h, w);
         boxBlurXY(t, h,  d, kernelSizeY3, highOffsetY, highOffsetY, h, w);
     }
     return true;
 }
 
+
+void SkBlurImageFilter::computeFastBounds(const SkRect& src, SkRect* dst) const {
+    if (getInput(0)) {
+        getInput(0)->computeFastBounds(src, dst);
+    } else {
+        *dst = src;
+    }
+
+    dst->outset(SkScalarMul(fSigma.width(), SkIntToScalar(3)),
+                SkScalarMul(fSigma.height(), SkIntToScalar(3)));
+}
 bool SkBlurImageFilter::filterImageGPU(Proxy* proxy, const SkBitmap& src, const SkMatrix& ctm,
                                        SkBitmap* result, SkIPoint* offset) {
 #if SK_SUPPORT_GPU
     SkBitmap input;
     if (!SkImageFilterUtils::GetInputResultGPU(getInput(0), proxy, src, ctm, &input, offset)) {
         return false;
     }
     GrTexture* source = input.getTexture();
     SkIRect rect;
     src.getBounds(&rect);
@@ skipping 10 matching lines @@
                                                              sigma.x(),
                                                              sigma.y()));
     offset->fX = rect.fLeft;
     offset->fY = rect.fTop;
     return SkImageFilterUtils::WrapTexture(tex, rect.width(), rect.height(), result);
 #else
     SkDEBUGFAIL("Should not call in GPU-less build");
     return false;
 #endif
 }