Cut reference from MountedDiskMonitor to DiskMountManager.

Cut reference from MountedDiskMonitor to DiskMountManager.

For number of reasons:

* The previous code implicitly relied on the fact that the Observer
events are notified to MountedDiskMonitor before VolumeManager
(otherwise VolumeManager::OnDiskEvent misses the hard-unplug event.)
It indeed holds, but it is not a part of explicit contract of base::ObserverList.
We should not rely on the detail.

* It simplifies MountedDiskMonitor (see the number of lines.)

* It simplifies the initialization process of VolumeManager/DiskMountManager,
i.e., removes duplicated RequestMountInfoRefresh calls.
This is desired for Bug 356583.

BUG=356583
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=281920

[kinaba, 2014-07-08 08:27:10]

On 2014/07/08 08:14:33, kinaba wrote:

Oops I forgot to include the updated test in the patchset. Updated now.

[hirono, 2014-07-08 08:54:56]

lgtm!

[kinaba, 2014-07-08 08:56:18]

The CQ bit was checked by kinaba@chromium.org

[kinaba, 2014-07-08 08:56:28]

The CQ bit was unchecked by kinaba@chromium.org

[kinaba, 2014-07-08 08:57:42]

The CQ bit was checked by kinaba@chromium.org

[commit-bot: I haz the power, 2014-07-08 08:58:14]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/kinaba@chromium.org/372853003/20001

[commit-bot: I haz the power, 2014-07-08 10:28:25]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  linux_chromium_chromeos_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_chrome...)

[commit-bot: I haz the power, 2014-07-08 11:32:01]

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

[commit-bot: I haz the power, 2014-07-08 11:32:02]

Try jobs failed on following builders:
  linux_chromium_chromeos_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_chrome...)

[kinaba, 2014-07-09 00:28:09]

The CQ bit was checked by kinaba@chromium.org

[commit-bot: I haz the power, 2014-07-09 00:30:17]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/kinaba@chromium.org/372853003/40001

[commit-bot: I haz the power, 2014-07-09 04:14:15]

Change committed as 281920