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

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: I60da46d57ac3b61e0b291e76f93460781d63dd47
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2017282Reviewed-by: Rohit Rao <rohitrao@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735286}

ios/chrome/browser/ui/tabs/tab_strip_controller_unittest.mm

@@ -33,7 +33,7 @@
 
 @interface TabStripControllerTestTabModel : NSObject
 
-@property(nonatomic, assign) ios::ChromeBrowserState* browserState;
+@property(nonatomic, assign) ChromeBrowserState* browserState;
 
 @end
 

ios/chrome/browser/ui/tabs/tab_strip_legacy_coordinator.h

@@ -7,12 +7,12 @@
 
 #import <UIKit/UIKit.h>
 
-#include "ios/chrome/browser/browser_state/chrome_browser_state_forward.h"
 #import "ios/chrome/browser/ui/coordinators/chrome_coordinator.h"
 #import "ios/chrome/browser/ui/tabs/requirements/tab_strip_highlighting.h"
 
 @protocol ApplicationCommands;
 @protocol BrowserCommands;
+class ChromeBrowserState;
 @protocol PopupMenuLongPressDelegate;
 @class TabModel;
 @protocol TabStripPresentation;
@@ -22,7 +22,7 @@
 @interface TabStripLegacyCoordinator : ChromeCoordinator<TabStripHighlighting>
 
 // BrowserState for this coordinator.
-@property(nonatomic, assign) ios::ChromeBrowserState* browserState;
+@property(nonatomic, assign) ChromeBrowserState* browserState;
 
 // Dispatcher for sending commands.
 @property(nonatomic, weak) id dispatcher;