[ios] Fix uses of ios::ChromeBrowserState in /ios/public/provider/chrome/browser/signin

The ChromeBrowserState has been moved from the "ios" namespace
to the global namespace by http://crrev.com/c/2014913. Fix the
uses from ios::ChromeBrowserState to ChromeBrowserState.

Also remove includes of chrome_browser_state_forward.h and use
a simple forward declaration instead (since the old name is no
longer necessary).

This CL was uploaded by git cl split.

R=jlebel@chromium.org

Bug: 1042208
Change-Id: Ie3c5d3607b588a916c3dd2345e0d0705106e053b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2017509
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Jérôme Lebel <jlebel@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734871}
4 files changed