mediaview: Support watchers in ArcFileSystemOperationRunner.

mediaview: Support watchers in ArcFileSystemOperationRunner.

AddWatcher() and RemoveWatcher() are added.
Also, ArcFileSystemOperationRunner implements FileSystemHost to
receive watcher callbacks from the Android container.

BUG=chromium:684233
TEST=trybot

Review-Url: https://codereview.chromium.org/2715493002
Cr-Commit-Position: refs/heads/master@{#454589}
(cherry picked from commit 1cf2cd5fd31329f2cb7de2cd2df919648b5e331b)

Review-Url: https://codereview.chromium.org/2736603002 .
Cr-Commit-Position: refs/branch-heads/3029@{#12}
Cr-Branched-From: 939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
Committed: https://chromium.googlesource.com/chromium/src/+/38e21206c01bdbb584ba2deb8dc23d5774755ccc

[Shuhei Takahashi, 2017-03-06 03:31:57]

Description was changed from

==========
mediaview: Support watchers in ArcFileSystemOperationRunner.

AddWatcher() and RemoveWatcher() are added.
Also, ArcFileSystemOperationRunner implements FileSystemHost to
receive watcher callbacks from the Android container.

BUG=chromium:684233
TEST=trybot

Review-Url: https://codereview.chromium.org/2715493002
Cr-Commit-Position: refs/heads/master@{#454589}
(cherry picked from commit 1cf2cd5fd31329f2cb7de2cd2df919648b5e331b)
==========

to

==========
mediaview: Support watchers in ArcFileSystemOperationRunner.

AddWatcher() and RemoveWatcher() are added.
Also, ArcFileSystemOperationRunner implements FileSystemHost to
receive watcher callbacks from the Android container.

BUG=chromium:684233
TEST=trybot

Review-Url: https://codereview.chromium.org/2715493002
Cr-Commit-Position: refs/heads/master@{#454589}
(cherry picked from commit 1cf2cd5fd31329f2cb7de2cd2df919648b5e331b)

Review-Url: https://codereview.chromium.org/2736603002 .
Cr-Commit-Position: refs/branch-heads/3029@{#12}
Cr-Branched-From:
939b32ee5ba05c396eef3fd992822fcca9a2e262-refs/heads/master@{#454471}
Committed:
https://chromium.googlesource.com/chromium/src/+/38e21206c01bdbb584ba2deb8dc2...
==========

[Shuhei Takahashi, 2017-03-06 03:31:58]

Committed patchset #1 (id:1) manually as
38e21206c01bdbb584ba2deb8dc23d5774755ccc.