[Media Router] Reland of "Media Router GYP/GN cleanup".

[Media Router] Reland of "Media Router GYP/GN cleanup".

Removed extra 'dependency' on target 'media_router_test_support'.

Also removed the ':' on some local dependencies.

Original patch: https://codereview.chromium.org/1136623003/
Original patch description:

- Refactor GYP and GN files to share source lists.
- Extract a proper test_support target.
- Fix upstream files with new target structure.

BUG=461815, 464199, 464205
TEST=Linux trybots. It's not clear to be exactly which bot, since
original patch failed after getting through trybots/CQ.

Committed: https://crrev.com/b6b09239feb034d546976028a15c75404579d0bb
Cr-Commit-Position: refs/heads/master@{#330204}

[imcheng (use chromium acct), 2015-05-15 19:06:18]

imcheng@google.com changed reviewers:
+ brettw@chromium.org

[imcheng (use chromium acct), 2015-05-15 19:06:19]

PTAL, thanks.

[brettw, 2015-05-15 21:24:15]

lgtm rubberstamp

[imcheng (use chromium acct), 2015-05-15 21:32:31]

Thanks Brett, submitting. +mfoltz as FYI.

[imcheng (use chromium acct), 2015-05-15 21:32:36]

The CQ bit was checked by imcheng@google.com

[commit-bot: I haz the power, 2015-05-15 21:35:18]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1122393005/40001

[commit-bot: I haz the power, 2015-05-15 21:42:03]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-05-18 11:27:52]

Patchset 3 (id:??) landed as
https://crrev.com/b6b09239feb034d546976028a15c75404579d0bb
Cr-Commit-Position: refs/heads/master@{#330204}