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

src/effects/SkXfermodeImageFilter.cpp

Index: src/effects/SkXfermodeImageFilter.cpp
diff --git a/src/effects/SkXfermodeImageFilter.cpp b/src/effects/SkXfermodeImageFilter.cpp
index 9692a2dd48de7ca514956bf0ca21840c11a7f2d1..6cedf840ed2927bb7c892aa6d0ca5d36f55563f5 100644
--- a/src/effects/SkXfermodeImageFilter.cpp
+++ b/src/effects/SkXfermodeImageFilter.cpp
@@ -130,8 +130,7 @@ bool SkXfermodeImageFilter::filterImageGPU(Proxy* proxy,
                                            SkIPoint* offset) const {
     SkBitmap background = src;
     SkIPoint backgroundOffset = SkIPoint::Make(0, 0);
-    if (this->getInput(0) && 
-        !this->getInput(0)->getInputResultGPU(proxy, src, ctx, &background, &backgroundOffset)) {
+    if (!this->filterInputGPU(0, proxy, src, ctx, &background, &backgroundOffset)) {
         return false;
     }
 
@@ -143,8 +142,7 @@ bool SkXfermodeImageFilter::filterImageGPU(Proxy* proxy,
 
     SkBitmap foreground = src;
     SkIPoint foregroundOffset = SkIPoint::Make(0, 0);
-    if (this->getInput(1) && 
-        !this->getInput(1)->getInputResultGPU(proxy, src, ctx, &foreground, &foregroundOffset)) {
+    if (!this->filterInputGPU(1, proxy, src, ctx, &foreground, &foregroundOffset)) {
         return false;
     }
     GrTexture* foregroundTex = foreground.getTexture();