Image filters: refactor input GPU processing into filterInputGPU().

src/effects/SkLightingImageFilter.cpp

Index: src/effects/SkLightingImageFilter.cpp
diff --git a/src/effects/SkLightingImageFilter.cpp b/src/effects/SkLightingImageFilter.cpp
index 270c10f86b01bbd3981f0a71d11f134d5bf9f9d2..199bb4d684f8e3ab842f1f44d22126e8b3f75197 100644
--- a/src/effects/SkLightingImageFilter.cpp
+++ b/src/effects/SkLightingImageFilter.cpp
@@ -361,8 +361,7 @@ bool SkLightingImageFilterInternal::filterImageGPU(Proxy* proxy,
                                                    SkIPoint* offset) const {
     SkBitmap input = src;
     SkIPoint srcOffset = SkIPoint::Make(0, 0);
-    if (this->getInput(0) &&
-        !this->getInput(0)->getInputResultGPU(proxy, src, ctx, &input, &srcOffset)) {
+    if (!this->filterInputGPU(0, proxy, src, ctx, &input, &srcOffset)) {
         return false;
     }
     SkIRect bounds;