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

src/effects/SkMorphologyImageFilter.cpp

Index: src/effects/SkMorphologyImageFilter.cpp
diff --git a/src/effects/SkMorphologyImageFilter.cpp b/src/effects/SkMorphologyImageFilter.cpp
index af45c0d3a109febeb2e93c7cbba03001df75ce2c..5008ad18145aeb23a5062beae604402f33c8d7f6 100644
--- a/src/effects/SkMorphologyImageFilter.cpp
+++ b/src/effects/SkMorphologyImageFilter.cpp
@@ -239,6 +239,15 @@ bool SkDilateImageFilter::onFilterImage(Proxy* proxy,
     return this->filterImageGeneric(dilateXProc, dilateYProc, proxy, source, ctm, dst, offset);
 }
 
+void SkMorphologyImageFilter::computeFastBounds(const SkRect& src, SkRect* dst) const {
+    if (getInput(0)) {
+        getInput(0)->computeFastBounds(src, dst);
+    } else {
+        *dst = src;
+    }
+    dst->outset(SkIntToScalar(fRadius.width()), SkIntToScalar(fRadius.height()));
+}
+
 #if SK_SUPPORT_GPU
 
 ///////////////////////////////////////////////////////////////////////////////