[ios] Fix uses of ios::ChromeBrowserState in /ios/chrome/browser/ui/browser_container

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=rohitrao@chromium.org

Bug: 1042208
Change-Id: Id47c687129017c1b84c20fdac2964bbd66850ceb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2017345
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Rohit Rao <rohitrao@chromium.org>
Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735875}

ios/chrome/browser/ui/browser_container/browser_container_coordinator.h

@@ -18,8 +18,7 @@
 // The BrowserContainerCoordinator must be constructed with a Browser, so the
 // ChromeBrowserState initializer is unavailable.
 - (instancetype)initWithBaseViewController:(UIViewController*)viewController
-                              browserState:
-                                  (ios::ChromeBrowserState*)browserState
+                              browserState:(ChromeBrowserState*)browserState
     NS_UNAVAILABLE;
 
 // The view controller managing the container view.