Mark existing image filter entry points that will be going away with Deprecated

src/effects/SkImageSource.cpp

Index: src/effects/SkImageSource.cpp
diff --git a/src/effects/SkImageSource.cpp b/src/effects/SkImageSource.cpp
index 2686fcb6c6ca76eedc41c941fda4ed840ee6d0e3..e9c98dc6ff71b2191cb5496ffc73529c4d22c214 100644
--- a/src/effects/SkImageSource.cpp
+++ b/src/effects/SkImageSource.cpp
@@ -64,8 +64,8 @@ void SkImageSource::flatten(SkWriteBuffer& buffer) const {
     buffer.writeImage(fImage);
 }
 
-bool SkImageSource::onFilterImage(Proxy* proxy, const SkBitmap& src, const Context& ctx,
-                                  SkBitmap* result, SkIPoint* offset) const {
+bool SkImageSource::onFilterImageDeprecated(Proxy* proxy, const SkBitmap& src, const Context& ctx,
+                                            SkBitmap* result, SkIPoint* offset) const {
     SkRect dstRect;
     ctx.ctm().mapRect(&dstRect, fDstRect);
     SkRect bounds = SkRect::MakeIWH(fImage->width(), fImage->height());