[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..6fe70328ae0fe4ee17380e0da8104be3f29042bf 100644
--- a/ios/web/web_state/ui/crw_web_controller.mm
+++ b/ios/web/web_state/ui/crw_web_controller.mm
@@ -88,6 +88,7 @@
 #import "ios/web/web_state/ui/crw_swipe_recognizer_provider.h"
 #import "ios/web/web_state/ui/crw_web_controller.h"
 #import "ios/web/web_state/ui/crw_web_controller_container_view.h"
+#import "ios/web/web_state/ui/crw_web_view_navigation_proxy.h"
 #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"
@@ -1425,6 +1426,13 @@ const NSTimeInterval kSnapshotOverlayTransition = 0.5;
   return _webViewProxy.get();
 }
 
+- (id<CRWWebViewNavigationProxy>)webViewNavigationProxy {
+  if ([self.webView conformsToProtocol:@protocol(CRWWebViewNavigationProxy)]) {

[Eugene But (OOO till 7-30), 2017/06/30 00:59:53]

Sorry, should have mentioned in the previous round. Should this be a DCHECK
instead?

DCHECK(!self.webView || [self.webView
conformsToProtocol:@protocol(CRWWebViewNavigationProxy)]);

[danyao, 2017/06/30 14:51:43]

Done.

+    return static_cast<id<CRWWebViewNavigationProxy>>(self.webView);
+  }
+  return nil;
+}
+
 - (UIView*)viewForPrinting {
   // Printing is not supported for native controllers.
   return _webView;