[Merge M51][Downloads] BaseFile shouldn't read past the expected EOF for a stub file.

[Merge M51][Downloads] BaseFile shouldn't read past the expected EOF for a stub file.

The partial stub file may have more data than expected due to
discrepancy between persisted metadata and the intermediate file.
Currently we resolve this conflict in favor of persisted metadata and
truncate the partial file to match. In this case, BaseFile::Initialize()
-> BaseFile::CalculatePartialHash() ended up reading past teh expected
EOF for large intermediate files. Consequently, BaseFile would conclude
incorrectly that the partial file is too short.

This patch fixes this bug by correctly stopping reading prior to the
expected EOF.

R=svaldez@chromium.org
BUG=603330
Review URL: https://codereview.chromium.org/1887873002

Cr-Commit-Position: refs/heads/master@{#387370}
(cherry picked from commit aeeba88e199ca02307bf5dfb651c867cfdb94a16)

Committed: https://chromium.googlesource.com/chromium/src/+/2bb4bee49cf1ef7c9c19b4790f5caf80a77c3ccf

[asanka, 2016-05-10 04:18:11]

Description was changed from

==========
[Merge M51][Downloads] BaseFile shouldn't read past the expected EOF for a stub
file.

The partial stub file may have more data than expected due to
discrepancy between persisted metadata and the intermediate file.
Currently we resolve this conflict in favor of persisted metadata and
truncate the partial file to match. In this case, BaseFile::Initialize()
-> BaseFile::CalculatePartialHash() ended up reading past teh expected
EOF for large intermediate files. Consequently, BaseFile would conclude
incorrectly that the partial file is too short.

This patch fixes this bug by correctly stopping reading prior to the
expected EOF.

R=svaldez@chromium.org
BUG=603330

Review URL: https://codereview.chromium.org/1887873002

Cr-Commit-Position: refs/heads/master@{#387370}
(cherry picked from commit aeeba88e199ca02307bf5dfb651c867cfdb94a16)
==========

to

==========
[Merge M51][Downloads] BaseFile shouldn't read past the expected EOF for a stub
file.

The partial stub file may have more data than expected due to
discrepancy between persisted metadata and the intermediate file.
Currently we resolve this conflict in favor of persisted metadata and
truncate the partial file to match. In this case, BaseFile::Initialize()
-> BaseFile::CalculatePartialHash() ended up reading past teh expected
EOF for large intermediate files. Consequently, BaseFile would conclude
incorrectly that the partial file is too short.

This patch fixes this bug by correctly stopping reading prior to the
expected EOF.

R=svaldez@chromium.org
BUG=603330

Review URL: https://codereview.chromium.org/1887873002

Cr-Commit-Position: refs/heads/master@{#387370}
(cherry picked from commit aeeba88e199ca02307bf5dfb651c867cfdb94a16)

Committed:
https://chromium.googlesource.com/chromium/src/+/2bb4bee49cf1ef7c9c19b4790f5c...
==========

[asanka, 2016-05-10 04:18:13]

Committed patchset #1 (id:1) manually as
2bb4bee49cf1ef7c9c19b4790f5caf80a77c3ccf.