Add SkPngChunkReader.

src/codec/SkCodec.cpp

Index: src/codec/SkCodec.cpp
diff --git a/src/codec/SkCodec.cpp b/src/codec/SkCodec.cpp
index 071a4b837121301a34edce31dc51f96bd05e30bc..11eb1f98479461b7307695ac49d44cde6f85cecb 100644
--- a/src/codec/SkCodec.cpp
+++ b/src/codec/SkCodec.cpp
@@ -25,7 +25,6 @@ struct DecoderProc {
 };
 
 static const DecoderProc gDecoderProcs[] = {
-    { SkPngCodec::IsPng, SkPngCodec::NewFromStream },
 #if !defined(GOOGLE3)
     { SkJpegCodec::IsJpeg, SkJpegCodec::NewFromStream },
 #endif
@@ -36,7 +35,8 @@ static const DecoderProc gDecoderProcs[] = {
     { SkWbmpCodec::IsWbmp, SkWbmpCodec::NewFromStream }
 };
 
-SkCodec* SkCodec::NewFromStream(SkStream* stream) {
+SkCodec* SkCodec::NewFromStream(SkStream* stream,
+                                SkPngChunkReader* chunkReader) {
     if (!stream) {
         return nullptr;
     }
@@ -44,15 +44,24 @@ SkCodec* SkCodec::NewFromStream(SkStream* stream) {
     SkAutoTDelete<SkStream> streamDeleter(stream);
     
     SkAutoTDelete<SkCodec> codec(nullptr);
-    for (uint32_t i = 0; i < SK_ARRAY_COUNT(gDecoderProcs); i++) {
-        DecoderProc proc = gDecoderProcs[i];
-        const bool correctFormat = proc.IsFormat(stream);
-        if (!stream->rewind()) {
-            return nullptr;
-        }
-        if (correctFormat) {
-            codec.reset(proc.NewFromStream(streamDeleter.detach()));
-            break;
+    // PNG is special, since we want to be able to supply an SkPngChunkReader.
+    // But this code follows the same pattern as the loop.
+    const bool isPng = SkPngCodec::IsPng(stream);
+    if (!stream->rewind()) {
+        return NULL;
+    }
+    if (isPng) {
+        codec.reset(SkPngCodec::NewFromStream(streamDeleter.detach(), chunkReader));
+    } else {
+        for (DecoderProc proc : gDecoderProcs) {
+            const bool correctFormat = proc.IsFormat(stream);
+            if (!stream->rewind()) {
+                return nullptr;
+            }
+            if (correctFormat) {
+                codec.reset(proc.NewFromStream(streamDeleter.detach()));
+                break;
+            }
         }
     }
 
@@ -68,11 +77,11 @@ SkCodec* SkCodec::NewFromStream(SkStream* stream) {
     }
 }
 
-SkCodec* SkCodec::NewFromData(SkData* data) {
+SkCodec* SkCodec::NewFromData(SkData* data, SkPngChunkReader* reader) {
     if (!data) {
         return nullptr;
     }
-    return NewFromStream(new SkMemoryStream(data));
+    return NewFromStream(new SkMemoryStream(data), reader);
 }
 
 SkCodec::SkCodec(const SkImageInfo& info, SkStream* stream)