Add the code to delete the unused folder-shortcut data

Add the code to delete the unused folder-shortcut data

The data in chrome.storage.local had been used but is now no longer used. This patch adds the code to remove them, in order to save the limited user storage.

BUG=268784
TEST=Files.app launches without error in console.
R=mtomasz@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=215856

[yoshiki, 2013-08-06 05:15:39]

@mtomasz: PTAL. Thanks.

[mtomasz, 2013-08-06 05:19:50]

lgtm. Please make sure that it doesn't throw an error if the item is not found.

[yoshiki, 2013-08-06 05:25:37]

On 2013/08/06 05:19:50, mtomasz wrote:
> lgtm. Please make sure that it doesn't throw an error if the item is not
found.

Thanks. I checked and confirmed.

[commit-bot: I haz the power, 2013-08-06 05:26:44]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/yoshiki@chromium.org/22361002/3001

[yoshiki, 2013-08-06 08:38:19]

Committed patchset #2 manually as r215856 (presubmit successful).