Replace EncodeBitmap with an interface.

include/core/SkWriteBuffer.h

Index: include/core/SkWriteBuffer.h
diff --git a/include/core/SkWriteBuffer.h b/include/core/SkWriteBuffer.h
index 4dbe17b0d9fd4b6d03a3f9da11a4452c89a31e65..76ee7ae5e8c83c20f9e42026ed763fc1c9ad7b8d 100644
--- a/include/core/SkWriteBuffer.h
+++ b/include/core/SkWriteBuffer.h
@@ -12,6 +12,7 @@
 #include "SkData.h"
 #include "SkPath.h"
 #include "SkPicture.h"
+#include "SkPixelSerializer.h"
 #include "SkRefCnt.h"
 #include "SkWriter32.h"
 
@@ -87,21 +88,22 @@ public:
     /**
      * Set an SkBitmapHeap to store bitmaps rather than flattening.
      *
-     * Incompatible with an EncodeBitmap function. If an EncodeBitmap function is set, setting an
-     * SkBitmapHeap will set the function to NULL in release mode and crash in debug.
+     * Incompatible with an SkPixelSerializer. If an SkPixelSerializer is set,
+     * setting an SkBitmapHeap will set the SkPixelSerializer to NULL in release
+     * and crash in debug.
      */
     void setBitmapHeap(SkBitmapHeap*);
 
     /**
-     * Provide a function to encode an SkBitmap to an SkData. writeBitmap will attempt to use
-     * bitmapEncoder to store the SkBitmap. If the reader does not provide a function to decode, it
-     * will not be able to restore SkBitmaps, but will still be able to read the rest of the stream.
-     * bitmapEncoder will never be called with a NULL pixelRefOffset.
+     * Set an SkPixelSerializer to store an encoded representation of pixels,
+     * e.g. SkBitmaps.
      *
-     * Incompatible with the SkBitmapHeap. If an encoder is set fBitmapHeap will be set to NULL in
-     * release and crash in debug.
+     * TODO: Encode SkImage pixels as well.
+     *
+     * Incompatible with the SkBitmapHeap. If an encoder is set fBitmapHeap will
+     * be set to NULL in release and crash in debug.

[reed1, 2014/12/08 15:51:15]

// Calls ref on the serializer.

wonder if this guy should return its arg, they way we do in paint for refcnted
pargs?

[scroggo, 2014/12/08 18:09:31]

Done.
We could do that, but I think it only makes sense if we expect this to be called
directly by clients. My understanding is that the purpose of returning the arg
is so the caller can do:

writeBuffer.setPixelSerializer(serializer)->unref()

The only current use case is in SkPictureData, which did not have a ref on it,
so it has no reason to call unref().

      */
-    void setBitmapEncoder(SkPicture::EncodeBitmap bitmapEncoder);
+    void setPixelSerializer(SkPixelSerializer*);
 
 private:
     bool isValidating() const { return SkToBool(fFlags & kValidation_Flag); }
@@ -114,7 +116,7 @@ private:
     SkBitmapHeap* fBitmapHeap;
     SkRefCntSet* fTFSet;
 
-    SkPicture::EncodeBitmap fBitmapEncoder;
+    SkAutoTUnref<SkPixelSerializer> fPixelSerializer;
 };
 
 #endif // SkWriteBuffer_DEFINED