Revert of [ios] Removed back-forward navigation API from CRWWebController.

ios/web/web_state/ui/crw_web_controller.h

 // Copyright 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef IOS_WEB_WEB_STATE_UI_CRW_WEB_CONTROLLER_H_
 #define IOS_WEB_WEB_STATE_UI_CRW_WEB_CONTROLLER_H_
 
 #import <UIKit/UIKit.h>
 
 #import "ios/web/net/crw_request_tracker_delegate.h"
@@ skipping 84 matching lines @@
 // next creation.
 @property(nonatomic, readwrite, assign) BOOL usePlaceholderOverlay;
 
 // Returns the current page loading phase.
 @property(nonatomic, readonly) web::LoadPhase loadPhase;
 
 // The fraction of the page load that has completed as a number between 0.0
 // (nothing loaded) and 1.0 (fully loaded).
 @property(nonatomic, readonly) double loadingProgress;
 
+// Returns whether the page can navigate backwards or forwards.
+@property(nonatomic, readonly) BOOL canGoBack;
+@property(nonatomic, readonly) BOOL canGoForward;
+
 // Returns the x, y offset the content has been scrolled.
 @property(nonatomic, readonly) CGPoint scrollPosition;
 
 // Returns whether the top of the content is visible.
 @property(nonatomic, readonly) BOOL atTop;
 
 // YES if JavaScript dialogs, HTTP authentication dialogs and window.open
 // calls should be suppressed. Default is NO. When dialog is suppressed
 // |CRWWebDelegate webControllerDidSuppressDialog:| will be called.
 @property(nonatomic, assign) BOOL shouldSuppressDialogs;
@@ skipping 69 matching lines @@
 // Stops loading the page.
 - (void)stopLoading;
 
 // Causes the page to start loading immediately if there is a pending load;
 // normally if the web view has been paged out for memory reasons, loads are
 // started lazily the next time the view is displayed. This can be called to
 // bypass the lazy behavior. This is equivalent to calling -view, but should be
 // used when deliberately pre-triggering a load without displaying.
 - (void)triggerPendingLoad;
 
+// Navigate forwards or backwards by one page.
+- (void)goBack;
+- (void)goForward;
 // Navigates forwards or backwards by |delta| pages. No-op if delta is out of
 // bounds.
 - (void)goDelta:(int)delta;
 // Navigates to the item at the given |index|.
 - (void)goToItemAtIndex:(int)index;
 
 // Executes |script| in the web view, registering user interaction.
 - (void)executeUserJavaScript:(NSString*)script
             completionHandler:(web::JavaScriptResultBlock)completion;
 
@@ skipping 104 matching lines @@
 
 // Acts on a single message from the JS object, parsed from JSON into a
 // DictionaryValue. Returns NO if the format for the message was invalid.
 - (BOOL)respondToMessage:(base::DictionaryValue*)crwMessage
        userIsInteracting:(BOOL)userIsInteracting
                originURL:(const GURL&)originURL;
 
 @end
 
 #endif  // IOS_WEB_WEB_STATE_UI_CRW_WEB_CONTROLLER_H_