Fix an issue that we didn't clean url request properly.

Fix an issue that we didn't clean url request properly.

The ByteStreamReader we used in DownloadFile does not support Close()
api, so we need to close the url request on UI thread if
"ByteStreamReader::Close" should be called.

Before we implement parallel download, we null out the callback on
ByteStreamReader during download interruption, and on UI thread, we
cancel the url request. But for parallel download, at some point, we
won't interrupt the download but need to cancel a particular request.

There is another CL that implements a browser test for parallel download and it will test the code here.
https://codereview.chromium.org/2819483002/

BUG=710576, 644352
Review-Url: https://codereview.chromium.org/2811293004
Cr-Commit-Position: refs/heads/master@{#465289}
(cherry picked from commit b444a98187571cf9ec627ac52fee7e81ffcecb93)

Review-Url: https://codereview.chromium.org/2828073002 .
Cr-Commit-Position: refs/branch-heads/3071@{#60}
Cr-Branched-From: a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed: https://chromium.googlesource.com/chromium/src/+/8cb70eaa5ea6568193561a95fc04bdcd4cd8fe4b

[xingliu, 2017-04-19 18:38:33]

Description was changed from

==========
Fix an issue that we didn't clean url request properly.

The ByteStreamReader we used in DownloadFile does not support Close()
api, so we need to close the url request on UI thread if
"ByteStreamReader::Close" should be called.

Before we implement parallel download, we null out the callback on
ByteStreamReader during download interruption, and on UI thread, we
cancel the url request. But for parallel download, at some point, we
won't interrupt the download but need to cancel a particular request.

There is another CL that implements a browser test for parallel download and it
will test the code here.
https://codereview.chromium.org/2819483002/

BUG=710576, 644352

Review-Url: https://codereview.chromium.org/2811293004
Cr-Commit-Position: refs/heads/master@{#465289}
(cherry picked from commit b444a98187571cf9ec627ac52fee7e81ffcecb93)
==========

to

==========
Fix an issue that we didn't clean url request properly.

The ByteStreamReader we used in DownloadFile does not support Close()
api, so we need to close the url request on UI thread if
"ByteStreamReader::Close" should be called.

Before we implement parallel download, we null out the callback on
ByteStreamReader during download interruption, and on UI thread, we
cancel the url request. But for parallel download, at some point, we
won't interrupt the download but need to cancel a particular request.

There is another CL that implements a browser test for parallel download and it
will test the code here.
https://codereview.chromium.org/2819483002/

BUG=710576, 644352

Review-Url: https://codereview.chromium.org/2811293004
Cr-Commit-Position: refs/heads/master@{#465289}
(cherry picked from commit b444a98187571cf9ec627ac52fee7e81ffcecb93)

Review-Url: https://codereview.chromium.org/2828073002 .
Cr-Commit-Position: refs/branch-heads/3071@{#60}
Cr-Branched-From:
a106f0abbf69dad349d4aaf4bcc4f5d376dd2377-refs/heads/master@{#464641}
Committed:
https://chromium.googlesource.com/chromium/src/+/8cb70eaa5ea6568193561a95fc04...
==========

[xingliu, 2017-04-19 18:38:34]

Committed patchset #1 (id:1) manually as
8cb70eaa5ea6568193561a95fc04bdcd4cd8fe4b.