Update PIEX version and adjust the RAW codec accordingly

src/codec/SkRawCodec.cpp

Index: src/codec/SkRawCodec.cpp
diff --git a/src/codec/SkRawCodec.cpp b/src/codec/SkRawCodec.cpp
index 762e82364cd3a6dd27e7c6534f69f0d40d6c8eb4..1247173b852c6a3bb03f8d89636b3f1233e5ecab 100644
--- a/src/codec/SkRawCodec.cpp
+++ b/src/codec/SkRawCodec.cpp
@@ -640,7 +640,11 @@ SkCodec* SkRawCodec::NewFromStream(SkStream* stream) {
     if (::piex::IsRaw(&piexStream)) {
         ::piex::Error error = ::piex::GetPreviewImageData(&piexStream, &imageData);
 
-        if (error == ::piex::Error::kOk && imageData.preview.length > 0) {
+        // PIEX can return JPEG compressed image or uncompressed RGB image. We only handle the JPEG

[scroggo, 2016/04/13 12:20:23]

I'm confused. What is the "uncompressed RGB image"? Isn't that what the DNG SDK
returns?

[yujieqin, 2016/04/13 13:11:29]

There are two kind of thumbnails image can be embeded into a RAW file:
* JPEG compressed
* plain uncompressed RGB data (e.g. DNG from mobile or some NEF contains
uncompressed thumbnail)

Before this change, PIEX only return image (thumbnail / preview) if it is JPEG
compressed. The uncompressed case will be ignore. 

The new PIEX can also return image (thumbnail / preview) if it is aplain
uncompressed RGB. We should add this format check here to ensure we only call
the JPEG codec if it is really a JPEG.

[scroggo, 2016/04/13 15:54:31]

Ah, this probably is more obvious to someone who is more familiar with piex.
Could you replace "image" with "thumbnail" in the comment? So it would instead
say:

PIEX can return JPEG compressed thumbnail or uncompressed RGB thumbnail

[yujieqin, 2016/04/14 07:54:59]

Actually it is not only for "thumbnail". Theoretically a preview can also be
"uncompressed", e.g. one can crate such DNG with little effort. That is why I
said "images".

In real world, we don't see any uncompressed preview case. And the current
change for PIEX is for getting uncompressed thumbnail only. We don't plan to add
support for uncompressed preview so far.

[scroggo, 2016/04/14 13:24:24]

Ah, thanks for clarifying.

+        // compressed case for now.
+        if (error == ::piex::Error::kOk && imageData.preview.length > 0 &&
+            imageData.preview.format == ::piex::Image::kJpegCompressed)
+        {
             // transferBuffer() is destructive to the rawStream. Abandon the rawStream after this
             // function call.
             // FIXME: one may avoid the copy of memoryStream and use the buffered rawStream.