[Extensions Toolbar] Make pref update non-destructive

[Extensions Toolbar] Make pref update non-destructive

A DCHECK in ToolbarActionsBar was triggering during a pref update, because the
visible number of icons was greater than the actual number of icons available
during a pref update. Fix this by making pref updates non-destructive; i.e.,
preserve current extension actions and simply move them around (this also
has the advantage of being less wasteful).

BUG=463736
Committed: https://crrev.com/6718fad588ac4818a12828d9c442d358b1021587
Cr-Commit-Position: refs/heads/master@{#322640}

[Devlin, 2015-03-26 15:39:40]

rdevlin.cronin@chromium.org changed reviewers:
+ finnur@chromium.org

[Devlin, 2015-03-26 15:39:47]

Patchset #1 (id:1) has been deleted

[Devlin, 2015-03-26 15:39:57]

Mind taking a look? :)

[Finnur, 2015-03-27 09:05:48]

LGTM, one nit.

https://codereview.chromium.org/1007083003/diff/20001/chrome/browser/ui/toolb...
File chrome/browser/ui/toolbar/toolbar_actions_bar_unittest.cc (right):

https://codereview.chromium.org/1007083003/diff/20001/chrome/browser/ui/toolb...
chrome/browser/ui/toolbar/toolbar_actions_bar_unittest.cc:418: // The order
should start as 0, 1, 2.
nit: Copy-paste error?

[Devlin, 2015-03-27 18:54:15]

https://codereview.chromium.org/1007083003/diff/20001/chrome/browser/ui/toolb...
File chrome/browser/ui/toolbar/toolbar_actions_bar_unittest.cc (right):

https://codereview.chromium.org/1007083003/diff/20001/chrome/browser/ui/toolb...
chrome/browser/ui/toolbar/toolbar_actions_bar_unittest.cc:418: // The order
should start as 0, 1, 2.
On 2015/03/27 09:05:48, Finnur wrote:
> nit: Copy-paste error?

Yep, thanks. :)

[Devlin, 2015-03-27 20:51:46]

The CQ bit was checked by rdevlin.cronin@chromium.org

[Devlin, 2015-03-27 20:51:46]

The patchset sent to the CQ was uploaded after l-g-t-m from finnur@chromium.org
Link to the patchset: https://codereview.chromium.org/1007083003/#ps40001
(title: "Fix comment")

[commit-bot: I haz the power, 2015-03-27 20:52:26]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1007083003/40001

[commit-bot: I haz the power, 2015-03-27 20:56:07]

Committed patchset #2 (id:40001)

[commit-bot: I haz the power, 2015-03-27 20:56:52]

Patchset 2 (id:??) landed as
https://crrev.com/6718fad588ac4818a12828d9c442d358b1021587
Cr-Commit-Position: refs/heads/master@{#322640}