[ios] Use chrome_browser_state_forward.h in /ios/chrome/browser/ui/content_suggestions

Instead of forward declaring ChromeBrowserState in the ios
namespace, use a header. This will allow moving the class
to the global namespace without having to change all the
forward declaration at the same time.

This CL was uploaded by git cl split.

R=gambard@chromium.org

Bug: 1042208
Change-Id: If065e4216e783e5356f4014696d2ebc853208f12
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2007726
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Gauthier Ambard <gambard@chromium.org>
Commit-Queue: Gauthier Ambard <gambard@chromium.org>
Cr-Commit-Position: refs/heads/master@{#733396}

ios/chrome/browser/ui/content_suggestions/content_suggestions_coordinator.h

@@ -5,12 +5,9 @@
 #ifndef IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_COORDINATOR_H_
 #define IOS_CHROME_BROWSER_UI_CONTENT_SUGGESTIONS_CONTENT_SUGGESTIONS_COORDINATOR_H_
 
+#include "ios/chrome/browser/browser_state/chrome_browser_state_forward.h"
 #import "ios/chrome/browser/ui/coordinators/chrome_coordinator.h"
 
-namespace ios {
-class ChromeBrowserState;
-}
-
 namespace web {
 class WebState;
 }

ios/chrome/browser/ui/content_suggestions/ntp_home_metrics.h

@@ -7,12 +7,9 @@
 
 #import "ios/chrome/browser/ui/content_suggestions/ntp_home_constant.h"
 
+#include "ios/chrome/browser/browser_state/chrome_browser_state_forward.h"
 #import "ios/chrome/browser/metrics/new_tab_page_uma.h"
 
-namespace ios {
-class ChromeBrowserState;
-}
-
 namespace web {
 class WebState;
 }