extensions: Cleanup class/struct fwd declarations

extensions: Cleanup class/struct fwd declarations

Remove useless class and struct forward declarations, and add
missing ones in extensions header files.

BUG=662195
Committed: https://crrev.com/12c9d49166df65545dd8cca1671891f048aea756
Cr-Commit-Position: refs/heads/master@{#434749}

[jbriance, 2016-11-28 15:52:56]

jbriance@cisco.com changed reviewers:
+ reillyg@chromium.org, rockot@chromium.org

[Ken Rockot(use gerrit already), 2016-11-28 20:09:37]

lgtm

[jbriance, 2016-11-28 20:16:08]

The CQ bit was checked by jbriance@cisco.com to run a CQ dry run

[commit-bot: I haz the power, 2016-11-28 20:17:42]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-28 22:26:27]

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

[commit-bot: I haz the power, 2016-11-28 22:26:28]

Dry run: This issue passed the CQ dry run.

[jbriance, 2016-11-28 22:26:40]

The CQ bit was checked by jbriance@cisco.com

[commit-bot: I haz the power, 2016-11-28 22:28:04]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-11-28 22:45:51]

CQ is committing da patch.

Bot data: {"patchset_id": 1, "attempt_start_ts": 1480372000575500, "parent_rev":
"02d2d0288819b8f4b502da139f8ee5743cc93c7a", "commit_rev":
"2a69e9d17d2ff9750913f24e556f62c984257b4c"}

[commit-bot: I haz the power, 2016-11-28 22:46:21]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-11-28 22:50:00]

Description was changed from

==========
extensions: Cleanup class/struct fwd declarations

Remove useless class and struct forward declarations, and add
missing ones in extensions header files.

BUG=662195
==========

to

==========
extensions: Cleanup class/struct fwd declarations

Remove useless class and struct forward declarations, and add
missing ones in extensions header files.

BUG=662195

Committed: https://crrev.com/12c9d49166df65545dd8cca1671891f048aea756
Cr-Commit-Position: refs/heads/master@{#434749}
==========

[commit-bot: I haz the power, 2016-11-28 22:50:01]

Patchset 1 (id:??) landed as
https://crrev.com/12c9d49166df65545dd8cca1671891f048aea756
Cr-Commit-Position: refs/heads/master@{#434749}