Revert of Add SkCodec, including PNG implementation.

include/codec/SkCodec.h

-/*
- * Copyright 2015 Google Inc.
- *
- * Use of this source code is governed by a BSD-style license that can be
- * found in the LICENSE file.
- */
-
-#ifndef SkCodec_DEFINED
-#define SkCodec_DEFINED
-
-#include "SkImageGenerator.h"
-#include "SkImageInfo.h"
-#include "SkSize.h"
-#include "SkTemplates.h"
-#include "SkTypes.h"
-
-class SkData;
-class SkStream;
-
-/**
- *  Abstraction layer directly on top of an image codec.
- */
-class SkCodec : public SkImageGenerator {
-public:
-    /**
-     *  If this stream represents an encoded image that we know how to decode,
-     *  return an SkCodec that can decode it. Otherwise return NULL.
-     *
-     *  If NULL is returned, the stream is deleted immediately. Otherwise, the
-     *  SkCodec takes ownership of it, and will delete it when done with it.
-     */
-    static SkCodec* NewFromStream(SkStream*);
-
-    /**
-     *  If this data represents an encoded image that we know how to decode,
-     *  return an SkCodec that can decode it. Otherwise return NULL.
-     *
-     *  Will take a ref if it returns a codec, else will not affect the data.
-     */
-    static SkCodec* NewFromData(SkData*);
-
-    /**
-     *  Return a size that approximately supports the desired scale factor.
-     *  The codec may not be able to scale efficiently to the exact scale
-     *  factor requested, so return a size that approximates that scale.
-     *
-     *  FIXME: Move to SkImageGenerator?
-     */
-    SkISize getScaledDimensions(float desiredScale) const;
-
-protected:
-    SkCodec(const SkImageInfo&, SkStream*);
-
-    /**
-     *  The SkAlphaType is a conservative answer. i.e. it is possible that it
-     *  initially returns a non-opaque answer, but completing the decode
-     *  reveals that the image is actually opaque.
-     */
-    bool onGetInfo(SkImageInfo* info) SK_OVERRIDE {
-        *info = fInfo;
-        return true;
-    }
-
-    // Helper for subclasses.
-    const SkImageInfo& getOriginalInfo() { return fInfo; }
-
-    virtual SkISize onGetScaledDimensions(float /* desiredScale */) const {
-        // By default, scaling is not supported.
-        return fInfo.dimensions();
-    }
-
-    /**
-     *  If the stream was previously read, attempt to rewind.
-     *  @returns:
-     *      true
-     *       - if the stream needed to be rewound, and the rewind
-     *         succeeded.
-     *       - if the stream did not need to be rewound.
-     *      false
-     *       - if the stream needed to be rewound, and rewind failed.
-     *  Subclasses MUST call this function before reading the stream (e.g. in
-     *  onGetPixels). If it returns false, onGetPixels should return
-     *  kCouldNotRewind.
-     */
-    bool SK_WARN_UNUSED_RESULT rewindIfNeeded();
-
-private:
-    const SkImageInfo fInfo;
-    SkAutoTDelete<SkStream> fStream;
-    bool fNeedsRewind;
-};
-#endif // SkCodec_DEFINED