Reland: Files.app: add create directory operation to context menu of directory tree.

Reland: Files.app: add create directory operation to context menu of directory tree.

Original CL:
> Files.app: add create directory operation to context menu of directory tree.
>
> Create directory operation is consisted with two operations,
> 1. Create new directory with default name.
> 2. Start rename operation of it.
>
> Since rename operation itself is already implemented with different CL,
> this CL focuses on to create new directory with default name and update
> the UI.
>
> BUG=502171
> TEST=browser_tests:DirectoryTreeContextMenu/FileManagerBrowserTest.Test/*
>
> Committed: https://crrev.com/57bd0537cd33f15039a9c6d929ce27f2515f8149
> Cr-Commit-Position: refs/heads/master@{#350522}

patch from issue 1353753002 at patchset 40001 (http://crrev.com/1353753002#ps40001)

Additional changes to the original CL:
* Waits an element before starting to input text in test case.

BUG=502171
TEST=run flaky test case 100 times; browser_tests:DirectoryTreeContextMenu/FileManagerBrowserTest.Test/18

Committed: https://crrev.com/2ea4d858f8e1b019aea2ef59d10b8efbcf0cda85
Cr-Commit-Position: refs/heads/master@{#351026}

[yawano, 2015-09-28 04:23:05]

yawano@chromium.org changed reviewers:
+ fukino@chromium.org

[yawano, 2015-09-28 04:23:05]

PTAL. Thank you!

[fukino, 2015-09-28 06:11:31]

On 2015/09/28 04:23:05, yawano wrote:
> PTAL. Thank you!

lgtm.
Please make sure this test runs without flakiness, for example by specifying
--gtest_repeat=100

[yawano, 2015-09-28 06:37:20]

On 2015/09/28 06:11:31, fukino wrote:
> On 2015/09/28 04:23:05, yawano wrote:
> > PTAL. Thank you!
> 
> lgtm.
> Please make sure this test runs without flakiness, for example by specifying
> --gtest_repeat=100

Thank you for the review! It passed --gtest_repeat=100!

[yawano, 2015-09-28 06:37:27]

The CQ bit was checked by yawano@chromium.org

[commit-bot: I haz the power, 2015-09-28 06:38:13]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1373733002/20001
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1373733002/20001

[commit-bot: I haz the power, 2015-09-28 06:43:11]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-09-28 06:43:55]

Patchset 2 (id:??) landed as
https://crrev.com/2ea4d858f8e1b019aea2ef59d10b8efbcf0cda85
Cr-Commit-Position: refs/heads/master@{#351026}