Revert of Reset the root layer on the compositor when recreating a root layer.

Revert of Reset the root layer on the compositor when recreating a root layer. (patchset #3 id:40001 of https://codereview.chromium.org/983933002/)

Reason for revert:
Unit test forgot to callTerminateContextFactoryForTests() and leaks memory.

Original issue's description:
> Reset the root layer on the compositor when recreating a root layer.
>
> This is going to be used by https://codereview.chromium.org/975943002/
>
> TEST=LayerOwnerTest.RecreateRootLayerWithNullCompositor
> TEST=LayerOwnerTest.RecreateRootLayerWithCompositor
>
> BUG=337596
>
> Committed: https://crrev.com/26d2ed6065c28b46c56a1266a6c7e28c9db55d45
> Cr-Commit-Position: refs/heads/master@{#319487}

TBR=sadrul@chromium.org,danakj@chromium.org,bruthig@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=337596
Committed: https://crrev.com/81a24564ab2fdeda4703559c93c39c4dc4746dcd
Cr-Commit-Position: refs/heads/master@{#319515}

[Lei Zhang, 2015-03-06 22:14:53]

Created Revert of Reset the root layer on the compositor when recreating a root
layer.

[commit-bot: I haz the power, 2015-03-06 22:15:56]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/984103003/1

[commit-bot: I haz the power, 2015-03-06 22:17:00]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-06 22:17:53]

Patchset 1 (id:??) landed as
https://crrev.com/81a24564ab2fdeda4703559c93c39c4dc4746dcd
Cr-Commit-Position: refs/heads/master@{#319515}