Move AppWindowContentsImpl to extensions

Move AppWindowContentsImpl to extensions

Remove unneeded include from app_window_contents.cc
Move app_window_contents.{cc,h} to extensions/browser/app_window
Change the namespace from apps to extensions.

BUG=403726
TBR=derat@chromium.org for include&namespace fix

Committed: https://crrev.com/5c34ceb43fe742c953e76f73052e9119705a71a6
Cr-Commit-Position: refs/heads/master@{#293094}

[hashimoto, 2014-09-01 05:03:18]

hashimoto@chromium.org changed reviewers:
+ benwells@chromium.org

[benwells, 2014-09-03 01:09:29]

lgtm

[hashimoto, 2014-09-03 04:05:58]

hashimoto@chromium.org changed reviewers:
+ derat@chromium.org

[hashimoto, 2014-09-03 04:05:59]

TBRing derat@chromium.org for include & namespace fix in
chrome/browser/power/process_power_collector_unittest.cc and
chrome/browser/ui/ash/launcher/chrome_launcher_controller_unittest.cc

[hashimoto, 2014-09-03 04:33:01]

The CQ bit was checked by hashimoto@chromium.org

[commit-bot: I haz the power, 2014-09-03 04:34:34]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/hashimoto@chromium.org/527693002/20001

[Daniel Erat, 2014-09-03 05:11:18]

lgtm

[Daniel Erat, 2014-09-03 05:11:19]

lgtm

lgtm

[commit-bot: I haz the power, 2014-09-03 07:38:13]

Committed patchset #2 (id:20001) as 36637ba97cad05364d348211edac5452075991e7

[commit-bot: I haz the power, 2014-09-10 03:24:18]

Patchset 2 (id:??) landed as
https://crrev.com/5c34ceb43fe742c953e76f73052e9119705a71a6
Cr-Commit-Position: refs/heads/master@{#293094}