Revert of Dispatch directory-changed event before rescan starts.

Revert of Dispatch directory-changed event before rescan starts. (patchset #1 id:1 of https://codereview.chromium.org/943473002/)

Reason for revert:
This CL broke as described in http://crbug.com/460398.
This issue is going to be fixed in different way with another CL.

Original issue's description:
> Dispatch directory-changed event before rescan starts.
>
> Directory rescan sometimes uses up IO and blocks other IOs which are necessary
> for updating the top-left breadcrumb. While this CL does not solve the real
> cause of the issue, this CL mitigates the problem by dispatching event earlier.
>
> BUG=459864
> TEST=manually tested as described in the issue
>
> Committed: https://crrev.com/3027da7aee006ad04e084690d6ea410a31969728
> Cr-Commit-Position: refs/heads/master@{#317021}

TBR=fukino@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=459864
Committed: https://crrev.com/afe477952010b25941baf77604ab2416b3b7dc28
Cr-Commit-Position: refs/heads/master@{#317264}

[yawano, 2015-02-20 07:27:35]

Created Revert of Dispatch directory-changed event before rescan starts.

[commit-bot: I haz the power, 2015-02-20 07:28:40]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/937423002/1

[fukino, 2015-02-20 07:28:44]

On 2015/02/20 07:27:35, yawano wrote:
> Created Revert of Dispatch directory-changed event before rescan starts.

lgtm

[commit-bot: I haz the power, 2015-02-20 07:29:12]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-02-20 07:29:49]

Patchset 1 (id:??) landed as
https://crrev.com/afe477952010b25941baf77604ab2416b3b7dc28
Cr-Commit-Position: refs/heads/master@{#317264}