[iOS] Refactoring web CRWSessionController user agent code.

ios/web/navigation/navigation_manager_impl.h

Index: ios/web/navigation/navigation_manager_impl.h
diff --git a/ios/web/navigation/navigation_manager_impl.h b/ios/web/navigation/navigation_manager_impl.h
index cf1b29562b7eca3487604784d65e6a613354ca0e..aea819392490ae638d10422210a5a372cdf69795 100644
--- a/ios/web/navigation/navigation_manager_impl.h
+++ b/ios/web/navigation/navigation_manager_impl.h
@@ -26,6 +26,14 @@ class NavigationManagerDelegate;
 class NavigationManagerFacadeDelegate;
 class SessionStorageBuilder;
 
+// |USER_INITIATED| represents pending item that is initiated by actual user

[Eugene But (OOO till 7-30), 2017/02/17 00:00:23]

Please move comment for enum values and place them before enum values and write
a comments to describe the enum itself (f.e. where it is used).

// Navigation was initiated by actual user action.
USER_INITIATED = 1,

// Navigation was initiated by renderer. Examples of renderer-initiated
navigations include:
//  * <a> link click
//  * changing window.location.href
//  * redirect via the <meta http-equiv="refresh"> tag
//  * using window.history.pushState
RENDERER_INITIATED

Please note that RENDERER_INITIATED is not the same as redirect and there is no
need to initialize second item (it is only needed when enum is used in UMA or
serialization and values should be stable).

[liaoyuke, 2017/02/17 01:16:51]

Thank you for the detailed explanation!

[Eugene But (OOO till 7-30), 2017/02/17 01:21:11]

Per my previous comment, please add comments for enum itself and remove  |= 2|

[liaoyuke, 2017/02/17 01:32:59]

Done.

+// actions, while |RENDERER_INITIATED| stands for pending item that is initiated
+// by Url redirect from another navigation item.
+enum class ItemInitiationType {
+  USER_INITIATED = 1,
+  RENDERER_INITIATED = 2,
+};
+
 // Implementation of NavigationManager.
 // Generally mirrors upstream's NavigationController.
 class NavigationManagerImpl : public NavigationManager {
@@ -82,6 +90,16 @@ class NavigationManagerImpl : public NavigationManager {
                const Referrer& referrer,
                ui::PageTransition type);
 
+  // Adds a new item with the given url, referrer, navigation type, pending item
+  // type, making it the current item. If pending item is the same as the

[Eugene But (OOO till 7-30), 2017/02/17 00:00:23]

s/current/pending

[liaoyuke, 2017/02/17 01:16:51]

Done.

+  // current item, this does nothing. |referrer| may be nil if there isn't one.
+  // The item starts out as pending, and will be lost unless
+  // |-commitPendingItem| is called.
+  void AddPendingItem(const GURL& url,
+                      const web::Referrer& referrer,
+                      ui::PageTransition navigation_type,
+                      ItemInitiationType initiation_type);
+
   // Convenience accessors to get the underlying NavigationItems from the
   // SessionEntries returned from |session_controller_|'s -lastUserEntry and
   // -previousEntry methods.
@@ -119,6 +137,7 @@ class NavigationManagerImpl : public NavigationManager {
   void GoForward() override;
   void GoToIndex(int index) override;
   void Reload(bool check_for_reposts) override;
+  void OverrideDesktopUserAgentForNextPendingItem() override;
 
   // Returns the current list of transient url rewriters, passing ownership to
   // the caller.
@@ -150,6 +169,12 @@ class NavigationManagerImpl : public NavigationManager {
   // |index| has ui::PAGE_TRANSITION_IS_REDIRECT_MASK.
   bool IsRedirectItemAtIndex(int index) const;
 
+  // If true, override navigation item's useDesktopUserAgent flag and always
+  // create the pending entry using the desktop user agent.
+  // TODO(crbug.com/692303): Remove this when overriding the user agent doesn't
+  // create a new NavigationItem.
+  bool override_desktop_user_agent_for_next_pending_item_;
+
   // The primary delegate for this manager.
   NavigationManagerDelegate* delegate_;