Remove //chrome deps from ExtensionDownloader

Remove //chrome deps from ExtensionDownloader

This frees ExtensionDownloader of any remaining
dependencies on //chrome in preparation for its
move to //extensions/browser.

The move is left for a follow-up CL.

BUG=398671
Committed: https://crrev.com/f2a6b62c728822b52356cd3385e41a5a36303ff0
Cr-Commit-Position: refs/heads/master@{#299776}

[Ken Rockot(use gerrit already), 2014-10-15 20:50:39]

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

[Ken Rockot(use gerrit already), 2014-10-15 20:50:39]

Yoyo, could you take a look?

[Yoyo Zhou, 2014-10-15 20:54:18]

LGTM

[Ken Rockot(use gerrit already), 2014-10-15 20:55:10]

The CQ bit was checked by rockot@chromium.org

[commit-bot: I haz the power, 2014-10-15 20:56:36]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/651403003/1

[commit-bot: I haz the power, 2014-10-15 21:58:20]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-10-15 21:59:11]

Patchset 1 (id:??) landed as
https://crrev.com/f2a6b62c728822b52356cd3385e41a5a36303ff0
Cr-Commit-Position: refs/heads/master@{#299776}