Revert of [ios] Switches ToolbarModelDelegateIOS to use WebStateList. (patchset #3 id:40001 of https://codereview.chromium.org/2770223003/ )

Reason for revert:
EG tests fail

https://luci-logdog.appspot.com/v/?s=chromium%2Fbb%2Fchromium.fyi%2FEarlGreyiOS%2F25732%2F%2B%2Frecipes%2Fsteps%2Fios_chrome_ui_egtests__iPhone_6s_iOS_10.0_%2F0%2Flogs%2Fcrash_report__2017-03-24-125038_%2F0

Original issue's description:
> [ios] Switches ToolbarModelDelegateIOS to use WebStateList.
>
> There is one method whose implementation still requires Tab and WebController.
> That method has been temporarily implemented using LegacyTabHelper to get the
> Tab for a WebState.
>
> BUG=None
>
> Review-Url: https://codereview.chromium.org/2770223003
> Cr-Commit-Position: refs/heads/master@{#459504}
> Committed: https://chromium.googlesource.com/chromium/src/+/5eb449e1e24522d224cc61be49c0cce7c48d05b3

TBR=sdefresne@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=None

Review-Url: https://codereview.chromium.org/2775943002
Cr-Commit-Position: refs/heads/master@{#459541}
9 files changed