Image filters: implement offsets in GPU path.

src/core/SkImageFilter.cpp

Index: src/core/SkImageFilter.cpp
diff --git a/src/core/SkImageFilter.cpp b/src/core/SkImageFilter.cpp
index 9f16b4a0c85e02d751cdf756eb1bf00dc3baad2c..33caf75a9d1e0a539e52cb0108c36344bc9386de 100644
--- a/src/core/SkImageFilter.cpp
+++ b/src/core/SkImageFilter.cpp
@@ -98,11 +98,12 @@ bool SkImageFilter::canFilterImageGPU() const {
     return this->asNewEffect(NULL, NULL);
 }
 
-bool SkImageFilter::filterImageGPU(Proxy* proxy, const SkBitmap& src, SkBitmap* result) {
+bool SkImageFilter::filterImageGPU(Proxy* proxy, const SkBitmap& src, SkBitmap* result,
+                                   SkIPoint* offset) {
 #if SK_SUPPORT_GPU
     SkBitmap input;
     SkASSERT(fInputCount == 1);
-    if (!SkImageFilterUtils::GetInputResultGPU(this->getInput(0), proxy, src, &input)) {
+    if (!SkImageFilterUtils::GetInputResultGPU(this->getInput(0), proxy, src, &input, offset)) {
         return false;
     }
     GrTexture* srcTexture = input.getTexture();