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

src/effects/SkMorphologyImageFilter.cpp

Index: src/effects/SkMorphologyImageFilter.cpp
diff --git a/src/effects/SkMorphologyImageFilter.cpp b/src/effects/SkMorphologyImageFilter.cpp
index 584cf1bf8c3db449240f2913be4eacfa4a213cfb..a5e680f405a945d99ca29f74a5abe3fe43892814 100644
--- a/src/effects/SkMorphologyImageFilter.cpp
+++ b/src/effects/SkMorphologyImageFilter.cpp
@@ -58,8 +58,7 @@ bool SkMorphologyImageFilter::filterImageGeneric(SkMorphologyImageFilter::Proc p
                                                  SkIPoint* offset) const {
     SkBitmap src = source;
     SkIPoint srcOffset = SkIPoint::Make(0, 0);
-    if (this->getInput(0) &&
-        !this->getInput(0)->filterImage(proxy, source, ctx, &src, &srcOffset)) {
+    if (!this->filterInput(0, proxy, source, ctx, &src, &srcOffset)) {
         return false;
     }