[Navigation Experiment] Add WKBasedNavigationManagerImpl.

ios/web/web_state/ui/crw_web_controller.mm

Index: ios/web/web_state/ui/crw_web_controller.mm
diff --git a/ios/web/web_state/ui/crw_web_controller.mm b/ios/web/web_state/ui/crw_web_controller.mm
index 61ee232486bd3e1dae3e6285d49e8aae9157208e..a26bb901d9d89254b8d61318158f29d7e9968e8f 100644
--- a/ios/web/web_state/ui/crw_web_controller.mm
+++ b/ios/web/web_state/ui/crw_web_controller.mm
@@ -91,6 +91,7 @@
 #import "ios/web/web_state/ui/crw_web_view_proxy_impl.h"
 #import "ios/web/web_state/ui/crw_wk_navigation_states.h"
 #import "ios/web/web_state/ui/crw_wk_script_message_router.h"
+#import "ios/web/web_state/ui/web_view_navigation_proxy.h"
 #import "ios/web/web_state/ui/wk_back_forward_list_item_holder.h"
 #import "ios/web/web_state/ui/wk_web_view_configuration_provider.h"
 #import "ios/web/web_state/web_controller_observer_bridge.h"
@@ -1425,6 +1426,13 @@ const NSTimeInterval kSnapshotOverlayTransition = 0.5;
   return _webViewProxy.get();
 }
 
+- (id<WebViewNavigationProxy>)webViewNavigationProxy {
+  if ([self.webView conformsToProtocol:@protocol(WebViewNavigationProxy)]) {
+    return (id<WebViewNavigationProxy>)(self.webView);

[Eugene But (OOO till 7-30), 2017/06/29 22:28:02]

Please use C++ casting

[danyao, 2017/06/29 23:09:48]

Ah missed this since I thought C++ casting style guides don't apply to
Objective-C objects.

+  }
+  return nil;
+}
+
 - (UIView*)viewForPrinting {
   // Printing is not supported for native controllers.
   return _webView;