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

include/effects/SkBitmapSource.h

 /*
  * Copyright 2012 The Android Open Source Project
  *
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
 
 #ifndef SkBitmapSource_DEFINED
 #define SkBitmapSource_DEFINED
 
 #include "SkImageFilter.h"
 #include "SkBitmap.h"
 
 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)
 
 protected:
     explicit SkBitmapSource(SkFlattenableReadBuffer& buffer);
     virtual void flatten(SkFlattenableWriteBuffer&) const SK_OVERRIDE;
     virtual bool onFilterImage(Proxy*, const SkBitmap& src, const SkMatrix&,
                                SkBitmap* result, SkIPoint* offset) SK_OVERRIDE;
 
 private:
     SkBitmap fBitmap;
+    SkRect   fSrcRect, fDstRect;
     typedef SkImageFilter INHERITED;
 };
 
 #endif