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

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=eugenebut@chromium.org

Bug: 1042208
Change-Id: I0662606ee05132aaa3e9da65a25745f6e3b93e3b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2017344Reviewed-by: Eugene But <eugenebut@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#736287}

ios/chrome/browser/ui/overscroll_actions/overscroll_actions_controller.h

@@ -7,11 +7,11 @@
 
 #import <UIKit/UIKit.h>
 
-#include "ios/chrome/browser/browser_state/chrome_browser_state_forward.h"
 #import "ios/chrome/browser/ui/overscroll_actions/overscroll_actions_view.h"
 #import "ios/chrome/browser/ui/util/relaxed_bounds_constraints_hittest.h"
 #import "ios/web/public/ui/crw_web_view_scroll_view_proxy.h"
 
+class ChromeBrowserState;
 @protocol CRWWebViewProxy;
 @class OverscrollActionsController;
 
@@ -96,7 +96,7 @@ extern NSString* const kOverscrollActionsDidEnd;
 // properly.
 @property(nonatomic, weak) id<OverscrollActionsControllerDelegate> delegate;
 // The BrowserState.
-@property(nonatomic, assign) ios::ChromeBrowserState* browserState;
+@property(nonatomic, assign) ChromeBrowserState* browserState;
 
 // Used to clear state maintained by the controller and de-register from
 // notifications. After this call the controller ceases to function and will