Ensure that FileSelectHelper is destroyed on the UI thread.

Ensure that FileSelectHelper is destroyed on the UI thread.

R=sky
BUG=563932
Committed: https://crrev.com/bbf7f34c9184e6c5b20a6d24096addb85a6a9f42
Cr-Commit-Position: refs/heads/master@{#370787}

[asanka, 2016-01-21 01:34:04]

sky: PTAL?

Explanation is in https://code.google.com/p/chromium/issues/detail?id=563932#c1
which is basically that it's possible for the final reference to a
FileSelectHelper object to be released on a thread other than the UI thread.

[sky, 2016-01-21 18:06:28]

LGTM

https://codereview.chromium.org/1616563002/diff/20001/chrome/browser/file_sel...
File chrome/browser/file_select_helper.h (right):

https://codereview.chromium.org/1616563002/diff/20001/chrome/browser/file_sel...
chrome/browser/file_select_helper.h:45:
content::BrowserThread::DeleteOnUIThread>,
Please add a comment as to why this needs to be destroyed on the ui thread.

[asanka, 2016-01-21 20:29:13]

The CQ bit was checked by asanka@chromium.org

[asanka, 2016-01-21 20:29:14]

The patchset sent to the CQ was uploaded after l-g-t-m from sky@chromium.org
Link to the patchset: https://codereview.chromium.org/1616563002/#ps40001
(title: "Add a comment describing why FileSelectHelper needs to be destroyed on
the UI thread.")

[asanka, 2016-01-21 20:29:41]

sky: thanks!

[commit-bot: I haz the power, 2016-01-21 20:30:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1616563002/40001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1616563002/40001

[commit-bot: I haz the power, 2016-01-21 21:21:10]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2016-01-21 21:22:29]

Description was changed from

==========
Ensure that FileSelectHelper is destroyed on the UI thread.

R=sky
BUG=563932
==========

to

==========
Ensure that FileSelectHelper is destroyed on the UI thread.

R=sky
BUG=563932

Committed: https://crrev.com/bbf7f34c9184e6c5b20a6d24096addb85a6a9f42
Cr-Commit-Position: refs/heads/master@{#370787}
==========

[commit-bot: I haz the power, 2016-01-21 21:22:29]

Patchset 3 (id:??) landed as
https://crrev.com/bbf7f34c9184e6c5b20a6d24096addb85a6a9f42
Cr-Commit-Position: refs/heads/master@{#370787}