Introduce State to DriveIntegrationService.

Introduce State to DriveIntegrationService.

This is small refactoring of DriveIntegrationService by introducing State.
This is preparation of mount/enabled state migration of
DriveIntegrationSerivice. By the migration, DriveIntegrationService can be
obtained even before initialization. This CL supports the change.
Also, by this CL, FileSystem can be deleted even before Initialize() is called.

BUG=284972
TEST=Ran unit_tests
R=kinaba@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=222231

[hidehiko, 2013-09-09 18:13:19]

Thank you for your review in advance,
- hidehiko

[kinaba, 2013-09-10 00:39:06]

lgtm

[commit-bot: I haz the power, 2013-09-10 00:41:39]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hidehiko@chromium.org/23548025/1

[commit-bot: I haz the power, 2013-09-10 01:15:54]

Sorry for I got bad news for ya.
Compile failed with a clobber build on mac_rel.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_rel&nu...
Your code is likely broken or HEAD is junk. Please ensure your
code is not broken then alert the build sheriffs.
Look at the try server FAQ for more details.

[commit-bot: I haz the power, 2013-09-10 01:18:20]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hidehiko@chromium.org/23548025/1

[commit-bot: I haz the power, 2013-09-10 01:28:26]

Sorry for I got bad news for ya.
Compile failed with a clobber build on mac_rel.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_rel&nu...
Your code is likely broken or HEAD is junk. Please ensure your
code is not broken then alert the build sheriffs.
Look at the try server FAQ for more details.

[commit-bot: I haz the power, 2013-09-10 01:51:55]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hidehiko@chromium.org/23548025/1

[commit-bot: I haz the power, 2013-09-10 02:02:36]

Sorry for I got bad news for ya.
Compile failed with a clobber build on mac_rel.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_rel&nu...
Your code is likely broken or HEAD is junk. Please ensure your
code is not broken then alert the build sheriffs.
Look at the try server FAQ for more details.

[commit-bot: I haz the power, 2013-09-10 03:27:28]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hidehiko@chromium.org/23548025/1

[commit-bot: I haz the power, 2013-09-10 03:36:17]

Sorry for I got bad news for ya.
Compile failed with a clobber build on mac_rel.
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_rel&nu...
Your code is likely broken or HEAD is junk. Please ensure your
code is not broken then alert the build sheriffs.
Look at the try server FAQ for more details.

[commit-bot: I haz the power, 2013-09-10 05:54:17]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/hidehiko@chromium.org/23548025/1

[commit-bot: I haz the power, 2013-09-10 08:02:12]

Retried try job too often on mac_rel for step(s) telemetry_unittests
http://build.chromium.org/p/tryserver.chromium/buildstatus?builder=mac_rel&nu...

[hidehiko, 2013-09-10 09:04:00]

Committed patchset #1 manually as r222231 (presubmit successful).