Adds UMA for slow and fast back/forward WKWebController navigations.

ios/web/web_state/ui/crw_web_controller+protected.h

 // Copyright 2014 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_PROTECTED_H_
 #define IOS_WEB_WEB_STATE_UI_CRW_WEB_CONTROLLER_PROTECTED_H_
 
 #import "ios/web/web_state/ui/crw_web_controller.h"
 
 #include "base/mac/scoped_nsobject.h"
@@ skipping 203 matching lines @@
 // Updates the internal state and informs the delegate that any outstanding load
 // operations are cancelled.
 - (void)loadCancelled;
 
 // Called when a load ends in an error.
 // TODO(stuartmorgan): Figure out if there's actually enough shared logic that
 // this makes sense. At the very least remove inMainFrame since that only makes
 // sense for UIWebView.
 - (void)handleLoadError:(NSError*)error inMainFrame:(BOOL)inMainFrame;
 
+// YES if a fast navigation can be performed using WKBackForwardList.
+- (BOOL)canPerformFastNavigationForSessionEntry:(CRWSessionEntry*)sessionEntry;
+
 #pragma mark - Internal methods for use by subclasses
 
 // The web view's view of the current URL. During page transitions
 // this may not be the same as the session history's view of the current URL.
 // This method can change the state of the CRWWebController, as it will display
 // an error if the returned URL is not reliable from a security point of view.
 // Note that this method is expensive, so it should always be cached locally if
 // it's needed multiple times in a method.
 @property(nonatomic, readonly) GURL currentURL;
 
@@ skipping 172 matching lines @@
 
 // Resets pending external request information.
 - (void)resetExternalRequest;
 
 // Converts MIME type string to WebViewDocumentType.
 - (web::WebViewDocumentType)documentTypeFromMIMEType:(NSString*)MIMEType;
 
 @end
 
 #endif  // IOS_WEB_WEB_STATE_UI_CRW_WEB_CONTROLLER_PROTECTED_H_