[Navigation Experiment] Add WKBasedNavigationManagerImpl.

ios/web/web_state/web_state_impl.mm

Index: ios/web/web_state/web_state_impl.mm
diff --git a/ios/web/web_state/web_state_impl.mm b/ios/web/web_state/web_state_impl.mm
index d918d551104742002c9fe8f0f0c4464aceed938f..f6292e5ba10164fd48ae34297b91ece698e735ab 100644
--- a/ios/web/web_state/web_state_impl.mm
+++ b/ios/web/web_state/web_state_impl.mm
@@ -18,6 +18,7 @@
 #import "ios/web/navigation/legacy_navigation_manager_impl.h"
 #import "ios/web/navigation/navigation_item_impl.h"
 #import "ios/web/navigation/session_storage_builder.h"
+#import "ios/web/navigation/wk_based_navigation_manager_impl.h"
 #include "ios/web/public/browser_state.h"
 #import "ios/web/public/crw_session_storage.h"
 #import "ios/web/public/java_script_dialog_presenter.h"
@@ -37,6 +38,8 @@
 #import "ios/web/web_state/session_certificate_policy_cache_impl.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/web_view_navigation_proxy.h"
+#import "ios/web/web_state/ui/web_view_navigation_proxy_impl.h"
 #include "ios/web/webui/web_ui_ios_controller_factory_registry.h"
 #include "ios/web/webui/web_ui_ios_impl.h"
 #include "net/http/http_response_headers.h"
@@ -85,7 +88,9 @@ WebStateImpl::WebStateImpl(const CreateParams& params,
     session_storage_builder.ExtractSessionState(this, session_storage);
   } else {
     navigation_manager_ = base::WrapUnique<NavigationManagerImpl>(
-        new LegacyNavigationManagerImpl);
+        web::GetWebClient()->IsSlimNavigationManagerEnabled()
+            ? (NavigationManagerImpl*)(new WKBasedNavigationManagerImpl)

[Eugene But (OOO till 7-30), 2017/06/29 01:48:19]

Please use C++ casting. But do you even need to cast here? Can you use
base::MakeUnique instead?

[danyao, 2017/06/29 16:05:26]

The cast is needed because I want to use the ? : shorthand, which requires the
two arms of : to return the same type.

MakeUnique doesn't work here because we want to selectively make one of the
derived classes. We would still need the conditional selection.

I changed this to a proper if statement to avoid the casting. It's just a little
bit longer. Also tweaked the contract of
SessionStorageBuilder::ExtractSessionState to require the navigation manager to
be already allocated in the passed-in WebStateImpl. This way we only need to do
this conditional instantiation of navigation manager once in this class.

+            : (NavigationManagerImpl*)(new LegacyNavigationManagerImpl));
     certificate_policy_cache_ =
         base::MakeUnique<SessionCertificatePolicyCacheImpl>();
   }
@@ -737,4 +742,8 @@ WebState* WebStateImpl::GetWebState() {
   return this;
 }
 
+WebViewNavigationProxy* WebStateImpl::GetWebViewNavigationProxy() const {
+  return [web_controller_ webViewNavigationProxy];
+}
+
 }  // namespace web