Makes AKEYCODE_BACK map to VKEY_BROWSER_BACK

Makes AKEYCODE_BACK map to VKEY_BROWSER_BACK

Seems as though there is no reason for the old mapping, and
browser_back makes more sense.

R=jdduke@chromium.org

Committed: https://crrev.com/825db4cd54f4aad434dd737b80e4349634589092
Cr-Commit-Position: refs/heads/master@{#325635}

[jdduke (slow), 2015-04-16 23:34:16]

lgtm.

+aurimas to make sure I'm not missing some corner case here (Aurimas we
intercept "back" at the ContentViewCore level, so this change should be
harmless).

[jdduke (slow), 2015-04-16 23:35:03]

(Oops, actually adding aurimas this time)

+aurimas to make sure I'm not missing some corner case here (Aurimas we
intercept "back" at the ContentViewCore level, so this change should be
harmless).

[aurimas (slooooooooow), 2015-04-16 23:38:24]

aurimas@chromium.org changed reviewers:
+ aurimas@chromium.org

[aurimas (slooooooooow), 2015-04-16 23:38:25]

It seems reasonable to me. LGTM

[sky, 2015-04-17 15:02:15]

The CQ bit was checked by sky@chromium.org

[commit-bot: I haz the power, 2015-04-17 15:02:53]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1095483003/1

[commit-bot: I haz the power, 2015-04-17 15:08:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-04-17 15:08:57]

Patchset 1 (id:??) landed as
https://crrev.com/825db4cd54f4aad434dd737b80e4349634589092
Cr-Commit-Position: refs/heads/master@{#325635}