Image Filters: refactor all CPU input processing into a filterInput helper function.

src/effects/SkColorFilterImageFilter.cpp

Index: src/effects/SkColorFilterImageFilter.cpp
diff --git a/src/effects/SkColorFilterImageFilter.cpp b/src/effects/SkColorFilterImageFilter.cpp
index 46bad10ce346325e10382cb01558d48784ef9a8b..acdb6ab7a720db08e9f3ed37f22ee43cb55f2ef8 100644
--- a/src/effects/SkColorFilterImageFilter.cpp
+++ b/src/effects/SkColorFilterImageFilter.cpp
@@ -61,7 +61,7 @@ bool SkColorFilterImageFilter::onFilterImage(Proxy* proxy, const SkBitmap& sourc
                                              SkIPoint* offset) const {
     SkBitmap src = source;
     SkIPoint srcOffset = SkIPoint::Make(0, 0);
-    if (getInput(0) && !getInput(0)->filterImage(proxy, source, ctx, &src, &srcOffset)) {
+    if (!this->filterInput(0, proxy, source, ctx, &src, &srcOffset)) {
         return false;
     }