Add SkImageGenerator Interface

src/images/SkDecodingImageGenerator.h

Index: src/images/SkDecodingImageGenerator.h
diff --git a/src/images/SkDecodingImageGenerator.h b/src/images/SkDecodingImageGenerator.h
new file mode 100644
index 0000000000000000000000000000000000000000..682aeb619cee14c6d3593e6cde664a93ea79592b
--- /dev/null
+++ b/src/images/SkDecodingImageGenerator.h
@@ -0,0 +1,45 @@
+/*
+ * Copyright 2013 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#ifndef SkDecodingImageGenerator_DEFINED
+#define SkDecodingImageGenerator_DEFINED
+
+#include "SkImageGenerator.h"
+
+class SkBitmap;
+
+/**
+ * Calls into SkImageDecoder::DecodeMemoryToTarget to implement a
+ * SkImageGenerator
+ */
+class SkDecodingImageGenerator : public SkImageGenerator {
+public:
+    /*
+     *  The constructor will take a reference to the SkData.  The
+     *  destructor will unref() it.
+     */
+    SkDecodingImageGenerator(SkData* data);
+    virtual ~SkDecodingImageGenerator();
+
+    virtual SkData* refEncodedData() SK_OVERRIDE;
+
+    virtual bool getInfo(SkImageInfo* info) SK_OVERRIDE;
+
+    virtual bool getPixels(const SkImageInfo& info,
+                           void* pixels,
+                           size_t rowBytes) SK_OVERRIDE;
+
+    /**
+     *  Install the SkData into the destination bitmap, using a new
+     *  SkDiscardablePixelRef and a new SkDecodingImageGenerator.
+     */
+    static bool Install(SkData* data, SkBitmap* destination);
+
+private:
+    SkData* fData;
+};
+#endif  // SkDecodingImageGenerator_DEFINED