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

src/effects/SkMorphologyImageFilter.cpp

Index: src/effects/SkMorphologyImageFilter.cpp
diff --git a/src/effects/SkMorphologyImageFilter.cpp b/src/effects/SkMorphologyImageFilter.cpp
index f3ae6accd9100e1e2a48f9d5c17d595c9d65989a..6f6a1e15f7c6a3c06c80da4622f0a3ee519f4c2c 100644
--- a/src/effects/SkMorphologyImageFilter.cpp
+++ b/src/effects/SkMorphologyImageFilter.cpp
@@ -612,8 +612,7 @@ bool SkMorphologyImageFilter::filterImageGPUGeneric(bool dilate,
                                                     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;