Add SkImageGenerator Interface

src/images/SkDecodingImageGenerator.h

+/*
+ * 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"
+
+/**
+ * Calls into SkImageDecoder::DecodeMemoryToTarget to implement a
+ * SkImageGenerator
+ */
+class SkDecodingImageGenerator : public SkImageGenerator {
+public:
+    /*
+     * The constructor will take a reference to the SkData.
+     */
+    SkDecodingImageGenerator(SkData* data);
+    virtual ~SkDecodingImageGenerator();
+
+    /**
+     *  Return a ref to the encoded (i.e. compressed) representation,
+     *  of this data.  The caller is responsible for calling unref()
+     *  on the data when it is finished.
+     */
+    virtual SkData* refEncodedData() SK_OVERRIDE;
+
+    /**
+     *  Return some information about the image, allowing the owner fo
+     *  this ojbect to allocate pixels.
+     *
+     *  @return false if anything goes wrong.
+     */
+    virtual bool getInfo(SkImageInfo* info) SK_OVERRIDE;
+
+    /**
+     *  Decode into the given pixels, a block of memory of size at
+     *  least (info.fHeight - 1) * rowBytes + (info.fWidth *
+     *  bytesPerPixel)
+     *
+     *  @param info Should be identical to the info returned by
+     *         getInfo so that the implementation can confirm that the
+     *         caller knows what it is asking for (config, size).
+     *         This contract also allows the caller to specify
+     *         different output-configs, which the implementation can
+     *         decide to support or not.
+     *
+     *  @return false if anything goes wrong.
+     */
+    virtual bool getPixels(const SkImageInfo& info,

[Alpha Left Google, 2013/11/19 02:00:48]

There should be a frame index here for animated images.

PixelRef should now contains a reference to SkDecodingImageGenerator and a frame
index.

[hal.canary, 2013/11/19 02:06:29]

Alpha, you should make a subclass of SkImageGenerator in Blink which does what
you want.

+                           void* pixels,
+                           size_t rowBytes) SK_OVERRIDE;
+private:
+    SkData* fData;
+};
+#endif  // SkDecodingImageGenerator_DEFINED