Revert of Changed api to notify when watched directory is deleted.

Revert of Changed api to notify when watched directory is deleted. (patchset #16 id:300001 of https://codereview.chromium.org/658013002/)

Reason for revert:
Linux Chromium OS ASan LSan Tests (1) http://build.chromium.org/p/chromium.memory/builders/Linux%20Chromium%20OS%20ASan%20LSan%20Tests%20(1) started burning when this landed:

@@@STEP_LOG_LINE@OnFileChanged@Direct leak of 48 byte(s) in 3 object(s) allocated from:@@@
@@@STEP_LOG_LINE@OnFileChanged@    #0 0x579f3b in operator new(unsigned long) (/tmp/run_tha_testfLYqpC/out/Release/browser_tests+0x579f3b)@@@
@@@STEP_LOG_LINE@OnFileChanged@    #1 0x4a85629 in file_manager::(anonymous namespace)::CreateAndStartFilePathWatcher(base::FilePath const&, base::Callback\u003Cvoid (base::FilePath const&, bool)> const&) chrome/browser/chromeos/file_manager/file_watcher.cc:24:3@@@

Original issue's description:
> Changed api to notify when watched directory is deleted.
>
> BUG=423257
> TEST=out/Release/browser_tests --gtest_filter=FileManagerPrivateApiTest.OnFileChanged
>
> Committed: https://crrev.com/962dea43ddd90e7e4224a03fa3c36a421281abb7
> Cr-Commit-Position: refs/heads/master@{#301325}

TBR=mtomasz@chromium.org,yoshiki@chromium.org,yawano@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=423257
Committed: https://crrev.com/c9205ddc2489bd76aa4bdbdbc30bd38ab1b74e28
Cr-Commit-Position: refs/heads/master@{#301373}

[Avi (use Gerrit), 2014-10-27 16:03:56]

Created Revert of Changed api to notify when watched directory is deleted.

[commit-bot: I haz the power, 2014-10-27 16:05:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/676403003/1

[commit-bot: I haz the power, 2014-10-27 16:07:02]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-27 16:07:39]

Patchset 1 (id:??) landed as
https://crrev.com/c9205ddc2489bd76aa4bdbdbc30bd38ab1b74e28
Cr-Commit-Position: refs/heads/master@{#301373}