Rename extension action context menu option string "Manage" to "Manage Extensions"

Rename extension action context menu option string "Manage" to "Manage Extensions"

When right click on an extension browser action in the Omnibox, the contextual
drop down says "Manage", which is unclear. Make the string to be more specific
such as "Manage Extensions".
The string's casing matches the platform; i.e. "Manage Extensions" for Mac,
"Manage extensions" everywhere else.

grd file changes:
Modifying 1 line label and 1 line desc text each in title case and in non title
case responsible for the label in: chrome/app/generated_resources.grd

BUG=418691
R=rouslan@chromium.org

TEST=
1) Launch chrome and install few extensions.
2) Right click an extension and observe
3) The context menu option for managing extensions should be string
   "Manage Extensions" on MAC, "Manage extensions" everywhere else.

Committed: https://crrev.com/4b4b173612017d0e45c2be082fb6f23baa79dc2a
Cr-Commit-Position: refs/heads/master@{#300516}

Committed: https://crrev.com/2f4ca84a245d6eddb1ceac4d352922bd3e1ad119
Cr-Commit-Position: refs/heads/master@{#300673}

[shilpa.shri, 2014-10-16 04:30:57]

PTAL

UI team has verified string changes.
(http://code.google.com/p/chromium/issues/detail?id=418691#c2)

Thank you.

[please use gerrit instead, 2014-10-20 23:03:54]

Please change TBR=... to R=... in the description. In general, try not to use
TBR unless there's a good reason for it. Thanks!

[shilpa.shri, 2014-10-21 02:37:45]

On 2014/10/20 23:03:54, Rouslan Solomakhin wrote:
> Please change TBR=... to R=... in the description. In general, try not to use
> TBR unless there's a good reason for it. Thanks!

Changed, as per comment.

[please use gerrit instead, 2014-10-21 16:37:04]

The CQ bit was checked by rouslan@chromium.org

[please use gerrit instead, 2014-10-21 16:37:04]

lgtm

[commit-bot: I haz the power, 2014-10-21 16:38:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/659663004/1

[commit-bot: I haz the power, 2014-10-21 17:48:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-21 17:50:28]

Patchset 1 (id:??) landed as
https://crrev.com/4b4b173612017d0e45c2be082fb6f23baa79dc2a
Cr-Commit-Position: refs/heads/master@{#300516}

[shilpa.shri, 2014-10-22 11:11:32]

Patchset #3 (id:40001) has been deleted

[shilpa.shri, 2014-10-22 11:14:50]

As per http://code.google.com/p/chromium/issues/detail?id=418691#c6, changing
string "Managed Extensions" to "Manage Extensions" in patch set 2. 
CQing patch set #2.

[shilpa.shri, 2014-10-22 11:14:58]

The CQ bit was checked by shilpa.shri@samsung.com

[commit-bot: I haz the power, 2014-10-22 11:15:35]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/659663004/20001

[commit-bot: I haz the power, 2014-10-22 13:10:47]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2014-10-22 13:11:37]

Patchset 2 (id:??) landed as
https://crrev.com/2f4ca84a245d6eddb1ceac4d352922bd3e1ad119
Cr-Commit-Position: refs/heads/master@{#300673}