Remove CRWSessionController usage from BrowserViewController.

ios/web/public/navigation_manager.h

Index: ios/web/public/navigation_manager.h
diff --git a/ios/web/public/navigation_manager.h b/ios/web/public/navigation_manager.h
index 3cd75e3613e268ed9c5396ae3eb51473a30cde7d..25c1206f1f0c77e7e78dc5c4413e5bb8d820d488 100644
--- a/ios/web/public/navigation_manager.h
+++ b/ios/web/public/navigation_manager.h
@@ -9,6 +9,7 @@
 
 #import "base/mac/scoped_nsobject.h"
 #include "ios/web/public/browser_url_rewriter.h"
+#include "ios/web/public/navigation_item_list.h"
 #include "ios/web/public/referrer.h"
 #include "ui/base/page_transition_types.h"
 
@@ -149,12 +150,21 @@ class NavigationManager {
   // TODO(crbug.com/533848): Update to use size_t.
   virtual void GoToIndex(int index) = 0;
 
+  // Returns a list of all non-redirected NavigationItems whose index precedes
+  // or follows the current index.
+  virtual NavigationItemList GetBackwardItems() const = 0;

[Eugene But (OOO till 7-30), 2017/03/10 16:23:27]

Could you please add tests for these.

[kkhorimoto, 2017/03/10 23:02:20]

They already exist in crw_session_controller_unittest.mm.  I'll transfer them
over to NavigationManager unittests once the functionality is actually handled
by that class; currently it's just a pass-through to CRWSessionController.

+  virtual NavigationItemList GetForwardItems() const = 0;
+
   // Reloads the current item. If |check_for_repost| is true and the current
   // item has POST data the user is prompted to see if they really want to
   // reload the page. In nearly all cases pass in true.  If a transient item is
   // showing, initiates a new navigation to its URL.
   virtual void Reload(bool check_for_repost) = 0;
 
+  // Inserts copies of |other_controller|'s NavigationItems to the front of this

[Eugene But (OOO till 7-30), 2017/03/10 16:23:27]

NavigationController does not have this method, so do we need it in navigation
manager? This very method is used for preload feature. Do you know how preload
is implemented on other platforms? CopyStateFromAndPrune could be API we need.

[kkhorimoto, 2017/03/10 23:02:20]

Will do this on the other CL.

+  // session history.
+  virtual void InsertStateFromManager(const NavigationManager* manager) = 0;
+
   // Forces the pending item to be loaded using desktop user agent. Note that
   // the pending item may or may not already exist.
   // TODO(crbug.com/692303): Remove this when overriding the user agent doesn't