Rename infobar_close_button to btn_close.

Rename infobar_close_button to btn_close.

This asset is also used in internal repository.

BUG=453995
Committed: https://crrev.com/52a26e4cba347c56316b9a6d1d3669bd7aff97ec
Cr-Commit-Position: refs/heads/master@{#314115}

[aurimas (slooooooooow), 2015-01-31 00:13:14]

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

[aurimas (slooooooooow), 2015-01-31 00:13:14]

newt: PTAL

[newt (away), 2015-01-31 00:38:14]

On 2015/01/31 00:13:14, aurimas wrote:
> newt: PTAL

lgtm

[aurimas (slooooooooow), 2015-01-31 00:40:35]

The CQ bit was checked by aurimas@chromium.org

[aurimas (slooooooooow), 2015-01-31 00:40:36]

woot!

[commit-bot: I haz the power, 2015-01-31 00:41:57]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/886193002/1

[commit-bot: I haz the power, 2015-01-31 06:43:26]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-01-31 06:43:27]

Try jobs failed on following builders:
  win8_chromium_gn_rel on tryserver.chromium.win
(http://build.chromium.org/p/tryserver.chromium.win/builders/win8_chromium_gn_...)

[aurimas (slooooooooow), 2015-01-31 08:21:10]

The CQ bit was checked by aurimas@chromium.org

[commit-bot: I haz the power, 2015-01-31 08:22:38]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/886193002/1

[commit-bot: I haz the power, 2015-01-31 12:32:44]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-01-31 12:32:45]

Try jobs failed on following builders:
  win8_chromium_gn_rel on tryserver.chromium.win
(http://build.chromium.org/p/tryserver.chromium.win/builders/win8_chromium_gn_...)

[aurimas (slooooooooow), 2015-02-02 06:31:18]

The CQ bit was checked by aurimas@chromium.org

[commit-bot: I haz the power, 2015-02-02 06:31:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/886193002/1

[commit-bot: I haz the power, 2015-02-02 08:51:31]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-02 08:52:40]

Patchset 1 (id:??) landed as
https://crrev.com/52a26e4cba347c56316b9a6d1d3669bd7aff97ec
Cr-Commit-Position: refs/heads/master@{#314115}