Revert of Define MOJO_SHELL_CLIENT uniformly across content

Revert of Define MOJO_SHELL_CLIENT uniformly across content (patchset #3 id:40001 of https://codereview.chromium.org/1462753002/ )

Reason for revert:
Not needed.

Original issue's description:
> Define MOJO_SHELL_CLIENT uniformly across content
>
> Separated out of https://codereview.chromium.org/1452823003/
>
> TBR=jam@chromium.org
> http://crbug.com/551253
>
> Committed: https://crrev.com/5e739169f376c3bf9c2c35a4efa0ebb6cbb3a9ee
> Cr-Commit-Position: refs/heads/master@{#360514}

TBR=jam@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true

Committed: https://crrev.com/02a377770e28b7b6129435d2eb27d38ac53dd619
Cr-Commit-Position: refs/heads/master@{#360522}

[Ben Goodger (Google), 2015-11-19 04:34:52]

Created Revert of Define MOJO_SHELL_CLIENT uniformly across content

[commit-bot: I haz the power, 2015-11-19 04:35:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1455423002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1455423002/1

[commit-bot: I haz the power, 2015-11-19 04:37:13]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-11-19 04:38:03]

Patchset 1 (id:??) landed as
https://crrev.com/02a377770e28b7b6129435d2eb27d38ac53dd619
Cr-Commit-Position: refs/heads/master@{#360522}