Make extension APIs work in MimeHandlerView.

Make extension APIs work in MimeHandlerView.

This will make some zoom functionality work in pdf viewer as they rely on
tabs.setZoomSettings/tabs.setZoom.

BUG=416332
Test=Load chrome with --enable-mime-handler-view and --out-of-process-pdf
Navigate to a pdf file, see ctrl+/- or zooming through browser menu work.
Ctrl + wheel still doesn't work, will fix that in a follow up CL.

Committed: https://crrev.com/d610be6f1c292e500100f6a3579673add6b5905f
Cr-Commit-Position: refs/heads/master@{#296295}

[lazyboy, 2014-09-23 17:33:52]

lazyboy@chromium.org changed reviewers:
+ fsamuel@chromium.org

[Fady Samuel, 2014-09-23 17:38:17]

lgtm

[lazyboy, 2014-09-23 18:07:35]

The CQ bit was checked by lazyboy@chromium.org

[commit-bot: I haz the power, 2014-09-23 20:31:45]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/597653002/1

[commit-bot: I haz the power, 2014-09-23 22:36:27]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-09-23 22:36:29]

Exceeded time limit waiting for builds to trigger.

[lazyboy, 2014-09-23 23:00:16]

The CQ bit was checked by lazyboy@chromium.org

[commit-bot: I haz the power, 2014-09-23 23:01:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/597653002/1

[commit-bot: I haz the power, 2014-09-23 23:17:58]

Committed patchset #1 (id:1) as 41700b20e83cebe7a7b81884d63078e8628eb500

[commit-bot: I haz the power, 2014-09-23 23:18:29]

Patchset 1 (id:??) landed as
https://crrev.com/d610be6f1c292e500100f6a3579673add6b5905f
Cr-Commit-Position: refs/heads/master@{#296295}