Replace EncodeBitmap with an interface.

include/core/SkPixelSerializer.h

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkPixelSerializer_DEFINED
+#define SkPixelSerializer_DEFINED
+
+#include "SkRefCnt.h"
+
+class SkData;
+struct SkImageInfo;
+
+class SkPixelSerializer : public SkRefCnt {
+public:
+    // return true if you want to serialize the encoded data, false if you want another
+    // another version serialized
+    virtual bool useEncodedData(SkData*) = 0;
+    // If you want to encode these pixels, return the encoded data as an SkData
+    // return null if you want to serialize the raw pixels
+    virtual SkData* encodePixels(const SkImageInfo&, void* pixels, size_t rowBytes) = 0;
+};
+#endif // SkPixelSerializer_DEFINED