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

ios/web/web_state/ui/crw_web_controller.h

Index: ios/web/web_state/ui/crw_web_controller.h
diff --git a/ios/web/web_state/ui/crw_web_controller.h b/ios/web/web_state/ui/crw_web_controller.h
index 7a0d998a260dd2367f08efb155d0a47273dff5ad..911315b9f3851a5addc54f36cffb62bd999416d1 100644
--- a/ios/web/web_state/ui/crw_web_controller.h
+++ b/ios/web/web_state/ui/crw_web_controller.h
@@ -102,6 +102,10 @@
 // (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;
 
@@ -191,6 +195,9 @@
 // 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;