Revert "Make SkPngCodec only read as much of the stream as necessary"

This reverts commit 2c65d5161260f3d45a63dcd92229bd09c8a12d53.

Reason for revert: Causing failures in Google3 (https://test.corp.google.com/ui#cl=153703311&flags=CAMQAg==&id=OCL:153703311:BASE:153703364:1492695824938:4db2240d&t=//chrome/skia/dm_wrapper:dm_wrapper) and differences in Gold. This change was not intended to change the output.

Original change's description:
> Make SkPngCodec only read as much of the stream as necessary
> 
> Previously, SkPngCodec assumed that the stream only contained one
> image, which ended at the end of the stream. It read the stream in
> arbitrarily-sized chunks, and then passed that data to libpng for
> processing.
> 
> If a stream contains more than one image, this may result in reading
> beyond the end of the image, making future reads read the wrong data.
> 
> Now, SkPngCodec starts by reading 8 bytes at a time. After the
> signature, 8 bytes is enough to know which chunk is next and how many
> bytes are in the chunk.
> 
> When decoding the size, we stop when we reach IDAT, and when decoding
> the image, we stop when we reach IEND.
> 
> This manual parsing is necessary to support APNG, which is planned in
> the future. It also allows us to remove the SK_GOOGLE3_PNG_HACK, which
> was a workaround for reading more than necessary at the beginning of
> the image.
> 
> Add a test that simulates the issue, by decoding a special stream that
> reports an error if the codec attempts to read beyond the end.
> 
> Temporarily disable the partial decoding tests for png. A larger change
> will be necessary to get those working again, and no clients are
> currently relying on incrementally decoding PNGs (i.e. decode part of
> an image, then decode further with more data).
> 
> Bug: skia:5368
> BUG:34073812
> 
> Change-Id: If832f7b20565411226fb5be3c305a4d16bf9269d
> Reviewed-on: https://skia-review.googlesource.com/13900
> Commit-Queue: Leon Scroggins <scroggo@google.com>
> Reviewed-by: Matt Sarett <msarett@google.com>
> 

TBR=msarett@google.com,scroggo@google.com,reviews@skia.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Change-Id: I2f82e9960dda7bf5c646774df84320dadb7b930e
Reviewed-on: https://skia-review.googlesource.com/13971
Reviewed-by: Leon Scroggins <scroggo@google.com>
Commit-Queue: Leon Scroggins <scroggo@google.com>

1 files changed, 1 insertions, 4 deletions

diff --git a/tests/CodecPartialTest.cpp b/tests/CodecPartialTest.cpp
index c029922f71..20cd1d11f0 100644
--- a/tests/CodecPartialTest.cpp
+++ b/tests/CodecPartialTest.cpp
@@ -118,9 +118,6 @@ static void test_partial(skiatest::Reporter* r, const char* name, size_t minByte
 }
 
 DEF_TEST(Codec_partial, r) {
-#if 0
-    // FIXME (scroggo): SkPngCodec needs to use SkStreamBuffer in order to
-    // support incremental decoding.
     test_partial(r, "plane.png");
     test_partial(r, "plane_interlaced.png");
     test_partial(r, "yellow_rose.png");
@@ -131,7 +128,7 @@ DEF_TEST(Codec_partial, r) {
     test_partial(r, "arrow.png");
     test_partial(r, "randPixels.png");
     test_partial(r, "baby_tux.png");
-#endif
+
     test_partial(r, "box.gif");
     test_partial(r, "randPixels.gif", 215);
     test_partial(r, "color_wheel.gif");