Implement canComputeFastBounds() for image filters.

src/effects/SkColorFilterImageFilter.cpp

Index: src/effects/SkColorFilterImageFilter.cpp
diff --git a/src/effects/SkColorFilterImageFilter.cpp b/src/effects/SkColorFilterImageFilter.cpp
index 2eb720e5c4cfcf093f815522af66e2839ebfb04e..94b530da8d689bd2eb4f79cd644553aefa5bbdb4 100755
--- a/src/effects/SkColorFilterImageFilter.cpp
+++ b/src/effects/SkColorFilterImageFilter.cpp
@@ -98,6 +98,10 @@ bool SkColorFilterImageFilter::onIsColorFilterNode(SkColorFilter** filter) const
     return false;
 }
 
+bool SkColorFilterImageFilter::affectsTransparentBlack() const {
+    return fColorFilter->affectsTransparentBlack();
+}
+
 #ifndef SK_IGNORE_TO_STRING
 void SkColorFilterImageFilter::toString(SkString* str) const {
     str->appendf("SkColorFilterImageFilter: (");