Reduce unnecessary download interruptions due to parallel requests

Reduce unnecessary download interruptions due to parallel requests

If a parallel request fails to when response starts, it will interrupt the download.
However, the failure may be recoverable by the main requst.
And this issue may cause a download to never finish even if user resumes it.
This change fixes the issue by allowing the failure to passthrough to DownloadFileImpl.
So that DownloadFileImpl can check whether the failure is recoverable.
A side effect of this change is more we will create received_slice vector even if all parallel requests fails.
This can be addressed in later changes.

BUG=720057
TBR=dtrainor@chromium.org

Review-Url: https://codereview.chromium.org/2872943003
Cr-Original-Commit-Position: refs/heads/master@{#470994}
Review-Url: https://codereview.chromium.org/2881463003 .
Cr-Commit-Position: refs/branch-heads/3071@{#522}
Cr-Branched-From: a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed: https://chromium.googlesource.com/chromium/src/+/1882066650be756a0dc62dfdabf54bf1f3f9241b

[qinmin, 2017-05-12 00:13:05]

Description was changed from

==========
Reduce unnecessary download interruptions due to parallel requests

If a parallel request fails to when response starts, it will interrupt the
download.
However, the failure may be recoverable by the main requst.
And this issue may cause a download to never finish even if user resumes it.
This change fixes the issue by allowing the failure to passthrough to
DownloadFileImpl.
So that DownloadFileImpl can check whether the failure is recoverable.
A side effect of this change is more we will create received_slice vector even
if all parallel requests fails.
This can be addressed in later changes.

BUG=720057
TBR=dtrainor@chromium.org

Review-Url: https://codereview.chromium.org/2872943003
Cr-Commit-Position: refs/heads/master@{#470994}
(cherry picked from commit c41a4fc09f9356d7d225747454b707eccd745e54)
==========

to

==========
Reduce unnecessary download interruptions due to parallel requests

If a parallel request fails to when response starts, it will interrupt the
download.
However, the failure may be recoverable by the main requst.
And this issue may cause a download to never finish even if user resumes it.
This change fixes the issue by allowing the failure to passthrough to
DownloadFileImpl.
So that DownloadFileImpl can check whether the failure is recoverable.
A side effect of this change is more we will create received_slice vector even
if all parallel requests fails.
This can be addressed in later changes.

BUG=720057
TBR=dtrainor@chromium.org

Review-Url: https://codereview.chromium.org/2872943003
Cr-Original-Commit-Position: refs/heads/master@{#470994}
Review-Url: https://codereview.chromium.org/2881463003 .
Cr-Commit-Position: refs/branch-heads/3071@{#522}
Cr-Branched-From:
a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed:
https://chromium.googlesource.com/chromium/src/+/1882066650be756a0dc62dfdabf5...
==========

[qinmin, 2017-05-12 00:13:06]

Committed patchset #1 (id:1) manually as
1882066650be756a0dc62dfdabf54bf1f3f9241b (presubmit successful).