Implement srcRect and dstRect functionality in SkBitmapSource. This is required for the "preserveAs…

include/effects/SkBitmapSource.h

Index: include/effects/SkBitmapSource.h
diff --git a/include/effects/SkBitmapSource.h b/include/effects/SkBitmapSource.h
index 138987e701bb91d0529dc3e3b9bbe7fbdbc9c2a6..ab50c184c0de633d31228431c3d31f1ea616ecf7 100644
--- a/include/effects/SkBitmapSource.h
+++ b/include/effects/SkBitmapSource.h
@@ -13,7 +13,7 @@
 
 class SK_API SkBitmapSource : public SkImageFilter {
 public:
-    explicit SkBitmapSource(const SkBitmap& bitmap);
+    explicit SkBitmapSource(const SkBitmap& bitmap, const SkRect* srcRect = NULL, const SkRect* dstRect = NULL);

[reed1, 2013/12/05 18:48:25]

Two option params + explicit?

Can we make two (at least) different constuctors, if NULL, NULL is common, or
have none of them have default values?

Not sure it applies here, but SkCanvas' convention was that src was optional,
but dst was required (in which case it was & instead of *). Maybe that doesn't
apply here...

[Stephen White, 2013/12/05 18:59:54]

Yep, explicit is still needed since call sites of the 1-arg version can still be
interpreted as an implicit conversion.
Blink will shortly be calling only the 3-arg version. I'd like to keep the 1-arg
version around to keep tests concise. So I could do 1-arg and 3-arg, with all
parameters required. That would cover the known use cases. Not really sure about
the usefulness of the other two (src-only or dst-only). Maybe we could add them
later if needed.

 
     SK_DECLARE_PUBLIC_FLATTENABLE_DESERIALIZATION_PROCS(SkBitmapSource)
 
@@ -25,6 +25,7 @@ protected:
 
 private:
     SkBitmap fBitmap;
+    SkRect   fSrcRect, fDstRect;
     typedef SkImageFilter INHERITED;
 };