Revert 2.5 CLs that relate to pulling Extension port management out of messaging.js.

Revert 2.5 CLs that relate to pulling Extension port management out of messaging.js.

The first is 1be1629824f63c62466b44fc90d40101fa9d495a:
"Clear the onMessage and onDisconnect listeners when their Extension Port is destroyed."
which was a fix to the original patch.

The second, original patch is 32b3a84be9aa4f70e83bd47c2a5cb32f05ad7f7e:
"Move the Extension Port implementation out of messaging.js into its own file port.js."

This is the key patch, which has caused no end of trouble. The goal was noble:
to fix the myriad of bugs which messaging has due to being written in JS not
C++. It appears that the moral of the story is: this is impossible, and the
hole we've dug in over the last 5 years cannot be recovered from (without a
complete rewrite, I suppose).

The last .5 of a patch was one of the tests added in
b9dca05429b19ad398d1dbf7496b44a94ba0f306 which will no longer pass.

BUG=486715, 477323, 475536
R=rockot@chromium.org

Committed: https://crrev.com/e9eaf5d68e674ff1ce760a6304266de3a0219787
Cr-Commit-Position: refs/heads/master@{#329571}

[not at google - send to devlin, 2015-05-12 17:00:33]

kalman@chromium.org changed reviewers:
+ rockot@chromium.org

[Ken Rockot(use gerrit already), 2015-05-12 22:21:13]

yikes. lgtm

[not at google - send to devlin, 2015-05-13 01:11:08]

The CQ bit was checked by kalman@chromium.org

[commit-bot: I haz the power, 2015-05-13 01:11:27]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1131043003/20001

[commit-bot: I haz the power, 2015-05-13 02:30:14]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-13 02:31:03]

Patchset 2 (id:??) landed as
https://crrev.com/e9eaf5d68e674ff1ce760a6304266de3a0219787
Cr-Commit-Position: refs/heads/master@{#329571}