Revert of Remote assistance on Chrome OS Part IV - It2MeHost (patchset #12 id:700001...

Revert of Remote assistance on Chrome OS Part IV - It2MeHost (patchset #12 id:700001 of https://codereview.chromium.org/639233002/)

Reason for revert:
Reverting due to build failure on Linux Ozone builder.
http://build.chromium.org/p/chromium.chromiumos/builders/Linux%20ChromiumOS%20Ozone%20Builder/builds/6011

Original issue's description:
> Remote assistance on Chrome OS Part IV - It2MeHost
>
> This CL links the it2me host to the Chrome binary on ChromeOS
> behind a flag.
> The following changes are made to the it2me host so that it can be run in the browser process.
> 1. Initializes SSL server sockets and specific CPU media features on ChromeOS startup.
> 2. Fixes a crash in it2me shutdown by making It2meHost owns the ChromotingHostContext.
> 3. Replace the blocking shutdown wait on PolicyWatcher with a callback.
>    Implements policy_watcher on ChromeOS using policy services.
> 4. Re-use existing threads, url request context getters and policy service on ChromeOS.
> 5. Fixed a incorrect DCHECK regarding the color format of the frames captured on ChromeOS.
>
> BUG=334087
>
> Committed: https://crrev.com/54dde6f02d121ff745e66b57205583087ff720ec
> Cr-Commit-Position: refs/heads/master@{#302034}

TBR=jochen@chromium.org,dpolukhin@chromium.org,jamiewalch@chromium.org,kalman@chromium.org,rmsousa@chromium.org,rockot@chromium.org,wez@chromium.org,agl@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=334087

Review URL: https://codereview.chromium.org/686373002

Cr-Commit-Position: refs/heads/master@{#302036}