Return false if IPC isn't handled by OverlayManager

Return false if IPC isn't handled by OverlayManager

Followup to https://codereview.chromium.org/1631073002/ to make sure
that the OnMessageReceived returns false for unhandled IPC messages.

BUG=558602
Committed: https://crrev.com/d08d61d9490756258c84f0bb1d156e8e2e7ef0da
Cr-Commit-Position: refs/heads/master@{#371789}

[dnicoara, 2016-01-27 14:51:49]

The CQ bit was checked by dnicoara@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-01-27 14:51:56]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1640263002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1640263002/1

[dnicoara, 2016-01-27 14:52:01]

dnicoara@chromium.org changed reviewers:
+ rjkroege@chromium.org

[dnicoara, 2016-01-27 14:52:02]

PTAL

[commit-bot: I haz the power, 2016-01-27 15:12:21]

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

[commit-bot: I haz the power, 2016-01-27 15:12:21]

Dry run: This issue passed the CQ dry run.

[dnicoara, 2016-01-27 15:13:19]

dnicoara@chromium.org changed reviewers:
+ alexst@chromium.org

[dnicoara, 2016-01-27 15:13:19]

+alexst@

[alexst (slow to review), 2016-01-27 15:14:19]

lgtm

[dnicoara, 2016-01-27 15:14:39]

The CQ bit was checked by dnicoara@chromium.org

[commit-bot: I haz the power, 2016-01-27 15:14:44]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1640263002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1640263002/1

[commit-bot: I haz the power, 2016-01-27 15:18:59]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-01-27 15:20:06]

Description was changed from

==========
Return false if IPC isn't handled by OverlayManager

Followup to https://codereview.chromium.org/1631073002/ to make sure
that the OnMessageReceived returns false for unhandled IPC messages.

BUG=558602
==========

to

==========
Return false if IPC isn't handled by OverlayManager

Followup to https://codereview.chromium.org/1631073002/ to make sure
that the OnMessageReceived returns false for unhandled IPC messages.

BUG=558602

Committed: https://crrev.com/d08d61d9490756258c84f0bb1d156e8e2e7ef0da
Cr-Commit-Position: refs/heads/master@{#371789}
==========

[commit-bot: I haz the power, 2016-01-27 15:20:07]

Patchset 1 (id:??) landed as
https://crrev.com/d08d61d9490756258c84f0bb1d156e8e2e7ef0da
Cr-Commit-Position: refs/heads/master@{#371789}