Add DCHECKs for the touch selection menu runner singleton

Add DCHECKs for the touch selection menu runner singleton

This is to ensure that there exists at most one instance of the menu
runner simultaneously. This fix is now possible because of the
ViewsDelegate refactoring.

BUG=399721, 492991
Committed: https://crrev.com/20a7d9f7cf570609d5314fbc6ab3b1514b9e3308
Cr-Commit-Position: refs/heads/master@{#333747}

[mohsen, 2015-06-10 15:58:45]

mohsen@chromium.org changed reviewers:
+ sadrul@chromium.org

[mohsen, 2015-06-10 15:58:46]

Please take a look...

[sadrul, 2015-06-10 16:12:46]

lgtm

[mohsen, 2015-06-10 16:13:31]

The CQ bit was checked by mohsen@chromium.org

[commit-bot: I haz the power, 2015-06-10 16:13:50]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1173083002/1

[commit-bot: I haz the power, 2015-06-10 16:58:51]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-10 16:59:37]

Patchset 1 (id:??) landed as
https://crrev.com/20a7d9f7cf570609d5314fbc6ab3b1514b9e3308
Cr-Commit-Position: refs/heads/master@{#333747}

[Somcran80, 2017-05-16 22:54:00]

somcran80@gmail.com changed reviewers:
+ Somcran80@gmail.com