[Chromedriver] Retry deleting temp dir when needed

[Chromedriver] Retry deleting temp dir when needed

Occasionally ChromeDriver may fail to delete temporary directories
while exiting, causing wasted disk space. This change adds retry
logic while cleaning up these directories.

BUG=chromedriver:644
Review-Url: https://codereview.chromium.org/2853953002
Cr-Commit-Position: refs/heads/master@{#469199}
Committed: https://chromium.googlesource.com/chromium/src/+/7dfc58a73db333dc9b76adc2c6eb409b389a39bf

[johnchen, 2017-05-02 01:38:47]

johnchen@chromium.org changed reviewers:
+ stgao@chromium.org

[johnchen, 2017-05-02 01:38:48]

Shuotao: PTAL.

This CL fixes http://crbug.com/chromedriver/644, where ChromeDriver doesn't
always delete temp directories before exiting. The bug is caused by a race
condition: ChromeDriver only waits for the termination of the main Chrome
process, but some of Chrome's child processes might still be running and using
the temp directories. This bug only appears to affect Windows. Linux has no
problem deleting directories and files that are in use.

Ideally, ChromeDriver should wait for the termination of all the child and
grandchild processes started by the main Chrome process, however this isn't easy
to do, and is almost impossible to do reliably, as it requires enumerating all
processes on the machine and use parent-child relationships to re-construct the
process tree. So instead, the CL uses a "wait and retry" strategy, and should be
reliable enough for all practical purposes.

[stgao, 2017-05-03 20:16:50]

lgtm

https://codereview.chromium.org/2853953002/diff/1/chrome/test/chromedriver/ch...
File chrome/test/chromedriver/chrome/scoped_temp_dir_with_retry.cc (right):

https://codereview.chromium.org/2853953002/diff/1/chrome/test/chromedriver/ch...
chrome/test/chromedriver/chrome/scoped_temp_dir_with_retry.cc:15: DLOG(WARNING)
<< "Could not delete temp dir in dtor.";
nit: It's unclear what dtor means.

[johnchen, 2017-05-03 22:17:53]

The CQ bit was checked by johnchen@chromium.org

[johnchen, 2017-05-03 22:17:54]

The patchset sent to the CQ was uploaded after l-g-t-m from stgao@chromium.org
Link to the patchset: https://codereview.chromium.org/2853953002/#ps20001
(title: "Fix warning message")

[commit-bot: I haz the power, 2017-05-03 22:18:46]

CQ is trying da patch.

Follow status at:
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2017-05-03 23:26:58]

CQ is committing da patch.

Bot data: {"patchset_id": 20001, "attempt_start_ts": 1493849873870330,
"parent_rev": "ab4427bff1c8598dbe5dfb53ba4bc6016c1e5428", "commit_rev":
"7dfc58a73db333dc9b76adc2c6eb409b389a39bf"}

[commit-bot: I haz the power, 2017-05-03 23:27:13]

Description was changed from

==========
[Chromedriver] Retry deleting temp dir when needed

Occasionally ChromeDriver may fail to delete temporary directories
while exiting, causing wasted disk space. This change adds retry
logic while cleaning up these directories.

BUG=chromedriver:644
==========

to

==========
[Chromedriver] Retry deleting temp dir when needed

Occasionally ChromeDriver may fail to delete temporary directories
while exiting, causing wasted disk space. This change adds retry
logic while cleaning up these directories.

BUG=chromedriver:644

Review-Url: https://codereview.chromium.org/2853953002
Cr-Commit-Position: refs/heads/master@{#469199}
Committed:
https://chromium.googlesource.com/chromium/src/+/7dfc58a73db333dc9b76adc2c6eb...
==========

[commit-bot: I haz the power, 2017-05-03 23:27:19]

Committed patchset #2 (id:20001) as
https://chromium.googlesource.com/chromium/src/+/7dfc58a73db333dc9b76adc2c6eb...