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

src/effects/SkLightingImageFilter.cpp

Index: src/effects/SkLightingImageFilter.cpp
diff --git a/src/effects/SkLightingImageFilter.cpp b/src/effects/SkLightingImageFilter.cpp
index 32589e1826c8aee778a0bb8cac730e6f38b17348..161d0ec17c6fdcd3a57d596fea1db233c4e56282 100644
--- a/src/effects/SkLightingImageFilter.cpp
+++ b/src/effects/SkLightingImageFilter.cpp
@@ -1172,10 +1172,9 @@ bool SkDiffuseLightingImageFilter::onFilterImage(Proxy* proxy,
                                                  const Context& ctx,
                                                  SkBitmap* dst,
                                                  SkIPoint* offset) const {
-    SkImageFilter* input = getInput(0);
     SkBitmap src = source;
     SkIPoint srcOffset = SkIPoint::Make(0, 0);
-    if (input && !input->filterImage(proxy, source, ctx, &src, &srcOffset)) {
+    if (!this->filterInput(0, proxy, source, ctx, &src, &srcOffset)) {
         return false;
     }
 
@@ -1313,10 +1312,9 @@ bool SkSpecularLightingImageFilter::onFilterImage(Proxy* proxy,
                                                   const Context& ctx,
                                                   SkBitmap* dst,
                                                   SkIPoint* offset) const {
-    SkImageFilter* input = getInput(0);
     SkBitmap src = source;
     SkIPoint srcOffset = SkIPoint::Make(0, 0);
-    if (input && !input->filterImage(proxy, source, ctx, &src, &srcOffset)) {
+    if (!this->filterInput(0, proxy, source, ctx, &src, &srcOffset)) {
         return false;
     }