[ios] Use chrome_browser_state_forward.h in /ios/chrome/browser/history

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=sczs@chromium.org

Bug: 1042208
Change-Id: Ic94da0d49905274b80bf5c5e164dbb98f2936d2a
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2007744
Auto-Submit: Sylvain Defresne <sdefresne@chromium.org>
Commit-Queue: Sergio Collazos <sczs@chromium.org>
Reviewed-by: Sergio Collazos <sczs@chromium.org>
Cr-Commit-Position: refs/heads/master@{#734032}

ios/chrome/browser/history/history_service_factory.h

@@ -10,6 +10,7 @@
 #include "base/macros.h"
 #include "base/no_destructor.h"
 #include "components/keyed_service/ios/browser_state_keyed_service_factory.h"
+#include "ios/chrome/browser/browser_state/chrome_browser_state_forward.h"
 
 enum class ServiceAccessType;
 
@@ -18,9 +19,6 @@ class HistoryService;
 }
 
 namespace ios {
-
-class ChromeBrowserState;
-
 // Singleton that owns all HistoryServices and associates them with
 // ios::ChromeBrowserState.
 class HistoryServiceFactory : public BrowserStateKeyedServiceFactory {

ios/chrome/browser/history/top_sites_factory.h

@@ -9,15 +9,13 @@
 #include "base/memory/ref_counted.h"
 #include "base/no_destructor.h"
 #include "components/keyed_service/ios/refcounted_browser_state_keyed_service_factory.h"
+#include "ios/chrome/browser/browser_state/chrome_browser_state_forward.h"
 
 namespace history {
 class TopSites;
 }
 
 namespace ios {
-
-class ChromeBrowserState;
-
 // TopSitesFactory is a singleton that associates history::TopSites instance to
 // ChromeBrowserState.
 class TopSitesFactory : public RefcountedBrowserStateKeyedServiceFactory {

ios/chrome/browser/history/web_history_service_factory.h

@@ -10,15 +10,13 @@
 #include "base/macros.h"
 #include "base/no_destructor.h"
 #include "components/keyed_service/ios/browser_state_keyed_service_factory.h"
+#include "ios/chrome/browser/browser_state/chrome_browser_state_forward.h"
 
 namespace history {
 class WebHistoryService;
 }
 
 namespace ios {
-
-class ChromeBrowserState;
-
 // Singleton that owns all WebHistoryServices and associates them with
 // ios::ChromeBrowserState.
 class WebHistoryServiceFactory : public BrowserStateKeyedServiceFactory {