add encodeData() to SkImageEncoder, and add encoding to SkImage

include/images/SkImageEncoder.h

Index: include/images/SkImageEncoder.h
diff --git a/include/images/SkImageEncoder.h b/include/images/SkImageEncoder.h
index 2965c88805101e88040079910123829294d9a323..3d3203fd1b3232e023022851d7e9d7576a41a785 100644
--- a/include/images/SkImageEncoder.h
+++ b/include/images/SkImageEncoder.h
@@ -11,6 +11,7 @@
 #include "SkTypes.h"
 
 class SkBitmap;
+class SkData;
 class SkWStream;
 
 class SkImageEncoder {
@@ -42,6 +43,16 @@ public:
      * Calls the particular implementation's onEncode() method to
      * actually do the encoding.
      */
+    SkData* encodeData(const SkBitmap&, int quality);
+
+    /**
+     * Encode bitmap 'bm' in the desired format, writing results to
+     * file 'file', at quality level 'quality' (which can be in range
+     * 0-100).
+     *
+     * Calls the particular implementation's onEncode() method to
+     * actually do the encoding.
+     */
     bool encodeFile(const char file[], const SkBitmap& bm, int quality);
 
     /**