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

src/core/SkMatrixImageFilter.cpp

Index: src/core/SkMatrixImageFilter.cpp
diff --git a/src/core/SkMatrixImageFilter.cpp b/src/core/SkMatrixImageFilter.cpp
index 823647f3de4f18e2106d21dfde230812ef088d57..4370ddadee2e42b2d9ef909b55028066ba0ebb5f 100644
--- a/src/core/SkMatrixImageFilter.cpp
+++ b/src/core/SkMatrixImageFilter.cpp
@@ -53,7 +53,7 @@ bool SkMatrixImageFilter::onFilterImage(Proxy* proxy,
                                         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;
     }