Implement support for a Context parameter in image filters

src/effects/SkBitmapSource.cpp

Index: src/effects/SkBitmapSource.cpp
diff --git a/src/effects/SkBitmapSource.cpp b/src/effects/SkBitmapSource.cpp
index dd44be7cd68105fb4e0d6ae83a085c50f997c48c..6834e9e32e9b5ff46ab6e4c5c0f672c464a35ead 100644
--- a/src/effects/SkBitmapSource.cpp
+++ b/src/effects/SkBitmapSource.cpp
@@ -42,11 +42,11 @@ void SkBitmapSource::flatten(SkWriteBuffer& buffer) const {
     buffer.writeRect(fDstRect);
 }
 
-bool SkBitmapSource::onFilterImage(Proxy* proxy, const SkBitmap&, const SkMatrix& matrix,
+bool SkBitmapSource::onFilterImage(Proxy* proxy, const SkBitmap&, const Context& ctx,
                                    SkBitmap* result, SkIPoint* offset) const {
     SkRect bounds, dstRect;
     fBitmap.getBounds(&bounds);
-    matrix.mapRect(&dstRect, fDstRect);
+    ctx.ctm().mapRect(&dstRect, fDstRect);
     if (fSrcRect == bounds && dstRect == bounds) {
         // No regions cropped out or resized; return entire bitmap.
         *result = fBitmap;