Clearing Tabs and Observer list when TabModelBase is destroyed.

Clearing Tabs and Observer list when TabModelBase is destroyed.

When TabModelBase is destroyed, Tabs and Observers List should
be cleared to free any holding tabs and observers respectively.

BUG=None.

Committed: https://crrev.com/eacf155f2d41b79a64c9b4eca997e62ebc77b8cb
Cr-Commit-Position: refs/heads/master@{#292326}

[wajahat, 2014-08-27 15:03:13]

wajahat.s@samsung.com changed reviewers:
+ bauerb@chromium.org, yfriedman@chromium.org

[wajahat, 2014-08-27 15:03:13]

Please review.

[Bernhard Bauer, 2014-08-27 17:03:13]

lgtm

[Yaron, 2014-08-27 18:14:16]

lgtm

[wajahat, 2014-08-28 04:21:32]

The CQ bit was checked by wajahat.s@samsung.com

[commit-bot: I haz the power, 2014-08-28 04:22:27]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/wajahat.s@samsung.com/511903002/1

[wajahat, 2014-08-28 04:23:35]

wajahat.s@samsung.com changed reviewers:
+ jitendra.ks@samsung.com
- bauerb@chromium.org, yfriedman@chromium.org

[commit-bot: I haz the power, 2014-08-28 05:30:21]

Committed patchset #1 (id:1) as 91103f8e85da67f27833d1033d933cf4bc105a41

[commit-bot: I haz the power, 2014-09-10 02:57:44]

Patchset 1 (id:??) landed as
https://crrev.com/eacf155f2d41b79a64c9b4eca997e62ebc77b8cb
Cr-Commit-Position: refs/heads/master@{#292326}