Move ExtensionHost from src/chrome to src/extensions

Move ExtensionHost from src/chrome to src/extensions

This breaks another src/extensions -> src/chrome dependency.

* Mechanical file move.
* Clean up DEPS.
* Move pinch-to-zoom handling to ExtensionViewHost as it only applies to
  visible extension content.

No functional changes.

BUG=321341
TEST=browser_tests *Extension*
TBR=sky@chromium.org for header file rename across chrome/browser

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=258494

[James Cook, 2014-03-20 20:36:45]

yoz, can you rubber-stamp this?

The only non-mechanical changes are the DEPS cleanup and moving gesture-handling
from ExtensionHost to ExtensionViewHost.

If it looks good feel free to CQ it.

[Yoyo Zhou, 2014-03-20 21:21:37]

LGTM, awesome

[James Cook, 2014-03-20 22:05:19]

+rockot just as FYI.  This might conflict with your patch
https://codereview.chromium.org/201203006/ - we'll see who wins the CQ race.

[James Cook, 2014-03-20 22:05:27]

The CQ bit was checked by jamescook@chromium.org

[commit-bot: I haz the power, 2014-03-20 22:06:39]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jamescook@chromium.org/198703006/1

[commit-bot: I haz the power, 2014-03-20 22:12:42]

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

[commit-bot: I haz the power, 2014-03-20 22:12:42]

Try jobs failed on following builders:
  tryserver.chromium on linux_chromium_clang_dbg

[James Cook, 2014-03-20 22:14:09]

The CQ bit was checked by jamescook@chromium.org

[commit-bot: I haz the power, 2014-03-20 22:16:38]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/jamescook@chromium.org/198703006/1

[commit-bot: I haz the power, 2014-03-21 01:39:02]

Change committed as 258494