Fix an issue that download file is not deleted when clicking Replace button

Fix an issue that download file is not deleted when clicking Replace button

When enqueueing a file to Android DownloadManager, we delete the file if
user choose to overwrite.
But when using Chrome's network stack, we didn't remove the file.
This will reduce user's sdcard space during download.
And it also causes issues when user try to resume the download.
This CL deletes the file when user clicks the "Replace File" button.

BUG=602721
Committed: https://crrev.com/c0258fd32bb4bda3ab721d426c3c4a73177af861
Cr-Commit-Position: refs/heads/master@{#387368}

[qinmin, 2016-04-12 20:59:01]

qinmin@chromium.org changed reviewers:
+ changwan@chromium.org

[qinmin, 2016-04-12 20:59:01]

PTAL

[Changwan Ryu, 2016-04-14 00:57:20]

lgtm

[qinmin, 2016-04-14 17:01:37]

qinmin@chromium.org changed reviewers:
+ yfriedman@chromium.org

[qinmin, 2016-04-14 17:01:38]

+yfriedman for OWNER

[Yaron, 2016-04-14 17:27:30]

lgtm

[qinmin, 2016-04-14 17:36:38]

The CQ bit was checked by qinmin@chromium.org

[commit-bot: I haz the power, 2016-04-14 17:37:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1884783002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1884783002/1

[commit-bot: I haz the power, 2016-04-14 18:16:16]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-04-14 18:18:19]

Description was changed from

==========
Fix an issue that download file is not deleted when clicking Replace button

When enqueueing a file to Android DownloadManager, we delete the file if
user choose to overwrite.
But when using Chrome's network stack, we didn't remove the file.
This will reduce user's sdcard space during download.
And it also causes issues when user try to resume the download.
This CL deletes the file when user clicks the "Replace File" button.

BUG=602721
==========

to

==========
Fix an issue that download file is not deleted when clicking Replace button

When enqueueing a file to Android DownloadManager, we delete the file if
user choose to overwrite.
But when using Chrome's network stack, we didn't remove the file.
This will reduce user's sdcard space during download.
And it also causes issues when user try to resume the download.
This CL deletes the file when user clicks the "Replace File" button.

BUG=602721

Committed: https://crrev.com/c0258fd32bb4bda3ab721d426c3c4a73177af861
Cr-Commit-Position: refs/heads/master@{#387368}
==========

[commit-bot: I haz the power, 2016-04-14 18:18:20]

Patchset 1 (id:??) landed as
https://crrev.com/c0258fd32bb4bda3ab721d426c3c4a73177af861
Cr-Commit-Position: refs/heads/master@{#387368}