Add gear menu to /downloads and /external_storage.

Add gear menu to /downloads and /external_storage.

Before, only Drive had a gear menu. This menu contains remaining space and help item. For consistency, the same button should appear on any other volume, but without Drive related items. As a result, the help menu item as well as the remaining size are in one place for each volume.

TEST=Check the gear button in Downloads, Drive and some removeable media. It should contain only 2 items for non-Drive volumes: space and help. Check if space is correct.
BUG=172813
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=181841

[mtomasz, 2013-02-08 05:41:51]

@yoshiki: PTAL.

[yoshiki, 2013-02-08 06:15:38]

lgtm with nit

https://codereview.chromium.org/12221082/diff/1001/chrome/browser/resources/f...
File chrome/browser/resources/file_manager/js/drive_banners.js (right):

https://codereview.chromium.org/12221082/diff/1001/chrome/browser/resources/f...
chrome/browser/resources/file_manager/js/drive_banners.js:537: var node =
this.document_.querySelector('body');
You can use just "document.body".

[commit-bot: I haz the power, 2013-02-08 06:38:42]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mtomasz@chromium.org/12221082/6001

[commit-bot: I haz the power, 2013-02-08 10:54:17]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mtomasz@chromium.org/12221082/12001

[commit-bot: I haz the power, 2013-02-08 11:58:33]

Retried try job too often on mac_rel for step(s) content_unittests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_rel&nu...

[commit-bot: I haz the power, 2013-02-12 01:00:11]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/mtomasz@chromium.org/12221082/12001

[commit-bot: I haz the power, 2013-02-12 03:00:00]

Retried try job too often on mac_rel for step(s) browser_tests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_rel&nu...