Add SkPngChunkReader.

include/core/SkImageDecoder.h

Index: include/core/SkImageDecoder.h
diff --git a/include/core/SkImageDecoder.h b/include/core/SkImageDecoder.h
index f4ae78a378baa83cf02bf7401c419325b6386ab7..fdf8b54a2213b58c0df612d3d513cbaf59ed98f2 100644
--- a/include/core/SkImageDecoder.h
+++ b/include/core/SkImageDecoder.h
@@ -9,6 +9,7 @@
 #define SkImageDecoder_DEFINED
 
 #include "SkBitmap.h"
+#include "SkChunkReader.h"
 #include "SkImage.h"
 #include "SkRect.h"
 #include "SkRefCnt.h"
@@ -126,25 +127,8 @@ public:
     */
     bool getRequireUnpremultipliedColors() const { return fRequireUnpremultipliedColors; }
 
-    /** \class Peeker
-
-        Base class for optional callbacks to retrieve meta/chunk data out of
-        an image as it is being decoded.
-    */
-    class Peeker : public SkRefCnt {
-    public:
-        SK_DECLARE_INST_COUNT(Peeker)
-
-        /** Return true to continue decoding, or false to indicate an error, which
-            will cause the decoder to not return the image.
-        */
-        virtual bool peek(const char tag[], const void* data, size_t length) = 0;
-    private:
-        typedef SkRefCnt INHERITED;
-    };
-
-    Peeker* getPeeker() const { return fPeeker; }
-    Peeker* setPeeker(Peeker*);
+    SkChunkReader* getPeeker() const { return fPeeker; }
+    SkChunkReader* setPeeker(SkChunkReader*);
 
     /**
      *  By default, the codec will try to comply with the "pref" colortype
@@ -231,7 +215,7 @@ public:
         to allocate the memory from a cache, volatile memory, or even from
         an existing bitmap's memory.
 
-        If a Peeker is installed via setPeeker, it may be used to peek into
+        If a SkChunkReader is installed via setPeeker, it may be used to peek into
         meta data during the decode.
     */
     Result decode(SkStream*, SkBitmap* bitmap, SkColorType pref, Mode);
@@ -401,7 +385,7 @@ protected:
     SkColorType getPrefColorType(SrcDepth, bool hasAlpha) const;
 
 private:
-    Peeker*                 fPeeker;
+    SkChunkReader*          fPeeker;
     SkBitmap::Allocator*    fAllocator;
     int                     fSampleSize;
     SkColorType             fDefaultPref;   // use if fUsePrefTable is false