Fix fragmented image signature handling

Fix fragmented image signature handling

ImageDecoder::determineImageType() is currently only examining the first
buffer segment (getSomeData).  But the signature is not guaranteed to be contiguous,
nor do we ever re-consolidate the buffer after receiving more data.

As a consequence, when the signature is fragmented (e.g. due to a slow
image load), we cannot detect the image type - even after all the data is
later received.

Refactor determineImageType() to consolidate the signature when needed.

BUG=637556
R=pkasting@chromium.org,scroggo@chromium.org,schenney@chromium.org

Review-Url: https://codereview.chromium.org/2252723003
Cr-Commit-Position: refs/heads/master@{#412631}
(cherry picked from commit 1b80a74055acae8a0296afe644513f52e34dec79)

Committed: https://chromium.googlesource.com/chromium/src/+/560b2ab7f31013f1a0ad9f0c174cb1ccd267e132

[f(malita), 2016-08-19 00:02:23]

Description was changed from

==========
Fix fragmented image signature handling

ImageDecoder::determineImageType() is currently only examining the first
buffer segment (getSomeData).  But the signature is not guaranteed to be
contiguous,
nor do we ever re-consolidate the buffer after receiving more data.

As a consequence, when the signature is fragmented (e.g. due to a slow
image load), we cannot detect the image type - even after all the data is
later received.

Refactor determineImageType() to consolidate the signature when needed.

BUG=637556
R=pkasting@chromium.org,scroggo@chromium.org,schenney@chromium.org

Review-Url: https://codereview.chromium.org/2252723003
Cr-Commit-Position: refs/heads/master@{#412631}
(cherry picked from commit 1b80a74055acae8a0296afe644513f52e34dec79)
==========

to

==========
Fix fragmented image signature handling

ImageDecoder::determineImageType() is currently only examining the first
buffer segment (getSomeData).  But the signature is not guaranteed to be
contiguous,
nor do we ever re-consolidate the buffer after receiving more data.

As a consequence, when the signature is fragmented (e.g. due to a slow
image load), we cannot detect the image type - even after all the data is
later received.

Refactor determineImageType() to consolidate the signature when needed.

BUG=637556
TBR=pkasting@chromium.org,scroggo@chromium.org,schenney@chromium.org

Review-Url: https://codereview.chromium.org/2252723003
Cr-Commit-Position: refs/heads/master@{#412631}
(cherry picked from commit 1b80a74055acae8a0296afe644513f52e34dec79)
==========

[f(malita), 2016-08-19 00:04:29]

Manual cherry-pick of http://crrev.com/2252723003, fix-only.

Verified on a local 2785 build.

[Peter Kasting, 2016-08-19 00:05:09]

LGTM

[f(malita), 2016-08-19 00:08:08]

Description was changed from

==========
Fix fragmented image signature handling

ImageDecoder::determineImageType() is currently only examining the first
buffer segment (getSomeData).  But the signature is not guaranteed to be
contiguous,
nor do we ever re-consolidate the buffer after receiving more data.

As a consequence, when the signature is fragmented (e.g. due to a slow
image load), we cannot detect the image type - even after all the data is
later received.

Refactor determineImageType() to consolidate the signature when needed.

BUG=637556
TBR=pkasting@chromium.org,scroggo@chromium.org,schenney@chromium.org

Review-Url: https://codereview.chromium.org/2252723003
Cr-Commit-Position: refs/heads/master@{#412631}
(cherry picked from commit 1b80a74055acae8a0296afe644513f52e34dec79)
==========

to

==========
Fix fragmented image signature handling

ImageDecoder::determineImageType() is currently only examining the first
buffer segment (getSomeData).  But the signature is not guaranteed to be
contiguous,
nor do we ever re-consolidate the buffer after receiving more data.

As a consequence, when the signature is fragmented (e.g. due to a slow
image load), we cannot detect the image type - even after all the data is
later received.

Refactor determineImageType() to consolidate the signature when needed.

BUG=637556
R=pkasting@chromium.org,scroggo@chromium.org,schenney@chromium.org

Review-Url: https://codereview.chromium.org/2252723003
Cr-Commit-Position: refs/heads/master@{#412631}
(cherry picked from commit 1b80a74055acae8a0296afe644513f52e34dec79)

Committed:
https://chromium.googlesource.com/chromium/src/+/560b2ab7f31013f1a0ad9f0c174c...
==========

[f(malita), 2016-08-19 00:08:10]

Committed patchset #1 (id:1) manually as
560b2ab7f31013f1a0ad9f0c174cb1ccd267e132.