Remove unwanted decoder failure check present in DecodeToYUV.

third_party/WebKit/Source/platform/graphics/ImageFrameGenerator.cpp

Index: third_party/WebKit/Source/platform/graphics/ImageFrameGenerator.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/ImageFrameGenerator.cpp b/third_party/WebKit/Source/platform/graphics/ImageFrameGenerator.cpp
index 5ed0c32cb845f5c8a4052e7b3207a22688b238b1..b91bfbbfb32ea323d628afc243515e45998b6e66 100644
--- a/third_party/WebKit/Source/platform/graphics/ImageFrameGenerator.cpp
+++ b/third_party/WebKit/Source/platform/graphics/ImageFrameGenerator.cpp
@@ -169,11 +169,6 @@ bool ImageFrameGenerator::DecodeToYUV(SegmentReader* data,
                                       const SkISize component_sizes[3],
                                       void* planes[3],
                                       const size_t row_bytes[3]) {
-  // TODO (scroggo): The only interesting thing this uses from the
-  // ImageFrameGenerator is m_decodeFailed. Move this into
-  // DecodingImageGenerator, which is the only class that calls it.
-  if (decode_failed_)

[scroggo_chromium, 2017/06/15 14:50:33]

The motivation for this check is that if the image fails to decode the old
fashioned way, we don't want to bother attempting to decode to YUV.

The TODO you're removing is to move this whole method to a different class,
since it's not really related to ImageFrameGenerator. The method is only on
ImageFrameGenerator because of the above - we don't want to try to YUV decode if
the image is known to be broken. If we detect that another way, we can move the
method somewhere more appropriate.

[naga, 2017/06/15 15:05:25]

In the current code decode_failed_ variable is not related to yuv decoding.
This condition unnecessary. This condtion will never fail for jpeg to yuv
decoding

[scroggo_chromium, 2017/06/15 16:46:19]

I disagree. Here's how it's related: If decode_failed_ is true, that means we
attempted to decode it before, and we failed. Presumably YUV decoding will also
fail, so we do not bother trying.
We only attempt to decode to YUV if the image is complete. Would it be possible
to start decoding an image that is not complete, and then attempt to YUV decode
later? If so, I think we still want this check.

If it's not possible, where do we prevent it from happening?

If you're correct, and we don't need this check, then please move the code into
DecodingImageGenerator (its only caller). It is unrelated to the general purpose
of ImageFrameGenerator.

[naga, 2017/06/15 16:59:20]

decode_failed_ variable status is updated on
DecodeAndScale()->TryToResumeDecode(). 
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/platform/graph...


The above function called only in OnGetPixels(). This will not come under jpeg
to yuv decoding code flow.
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/platform/graph...

For yuv decoding we used to call onGetYUV8Planes().
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/platform/graph...

-    return false;
 
   TRACE_EVENT1("blink", "ImageFrameGenerator::decodeToYUV", "frame index",
                static_cast<int>(index));