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

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=stkhapugin@chromium.org

Bug: 1042208
Change-Id: If05cda0d522ef0c707f9b1e33d0631fb809843ab
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2017542Reviewed-by: Stepan Khapugin <stkhapugin@chromium.org>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#735268}

ios/chrome/browser/ui/omnibox/popup/omnibox_popup_coordinator.h

@@ -9,8 +9,7 @@
 
 #include <memory>
 
-#include "ios/chrome/browser/browser_state/chrome_browser_state_forward.h"
-
+class ChromeBrowserState;
 @class CommandDispatcher;
 @protocol OmniboxPopupPresenterDelegate;
 @protocol OmniboxFocuser;
@@ -25,7 +24,7 @@ class WebStateList;
 - (instancetype)init NS_UNAVAILABLE;
 
 // BrowserState.
-@property(nonatomic, assign) ios::ChromeBrowserState* browserState;
+@property(nonatomic, assign) ChromeBrowserState* browserState;
 // Positioner for the popup.
 @property(nonatomic, weak) id<OmniboxPopupPresenterDelegate> presenterDelegate;
 // Whether this coordinator has results to show.