Some cleanup in extensions/renderer/dispatcher.cc .

Some cleanup in the extensions renderer dispatcher.

Moved the requiring of guestview modules into a seperate helper function, including that of extensionOptions, which was previously left in the chrome renderer dispatcher.

BUG=466215
Committed: https://crrev.com/ab77a103bb1337af53d1179676d226ebd5ae9480
Cr-Commit-Position: refs/heads/master@{#320229}

[paulmeyer, 2015-03-11 18:43:29]

paulmeyer@chromium.org changed reviewers:
+ kalman@chromium.org

[paulmeyer, 2015-03-11 18:43:30]

+kalman@

[not at google - send to devlin, 2015-03-11 22:50:55]

sorry didn't notice this one. lgtm.

[paulmeyer, 2015-03-12 02:50:14]

The CQ bit was checked by paulmeyer@chromium.org

[commit-bot: I haz the power, 2015-03-12 02:51:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/986503004/1

[commit-bot: I haz the power, 2015-03-12 03:51:51]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-12 03:52:32]

Patchset 1 (id:??) landed as
https://crrev.com/ab77a103bb1337af53d1179676d226ebd5ae9480
Cr-Commit-Position: refs/heads/master@{#320229}