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

src/effects/SkDisplacementMapEffect.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 "SkDisplacementMapEffect.h"
 #include "SkFlattenableBuffers.h"
 #include "SkUnPreMultiply.h"
@@ skipping 228 matching lines @@
     colorBounds.offset(-colorOffset);
 
     computeDisplacement(fXChannelSelector, fYChannelSelector, scale, dst,
                         &displ, colorOffset - displOffset, &color, colorBounds);
 
     offset->fX = bounds.left();
     offset->fY = bounds.top();
     return true;
 }
 
+void SkDisplacementMapEffect::computeFastBounds(const SkRect& src, SkRect* dst) const {
+    if (getColorInput()) {
+        getColorInput()->computeFastBounds(src, dst);
+    } else {
+        *dst = src;
+    }
+}
+
 ///////////////////////////////////////////////////////////////////////////////
 
 #if SK_SUPPORT_GPU
 class GrGLDisplacementMapEffect : public GrGLEffect {
 public:
     GrGLDisplacementMapEffect(const GrBackendEffectFactory& factory,
                               const GrDrawEffect& drawEffect);
     virtual ~GrGLDisplacementMapEffect();
 
     virtual void emitCode(GrGLShaderBuilder*,
@@ skipping 322 matching lines @@
                                                         const GrGLCaps&) {
     const GrDisplacementMapEffect& displacementMap =
         drawEffect.castEffect<GrDisplacementMapEffect>();
 
     EffectKey xKey = displacementMap.xChannelSelector();
     EffectKey yKey = displacementMap.yChannelSelector() << SkDisplacementMapEffect::kKeyBits;
 
     return xKey | yKey;
 }
 #endif