Moved NavigationManagerImpl serialization out of CRWSessionController.

ios/web/web_state/web_state.mm

Index: ios/web/web_state/web_state.mm
diff --git a/ios/web/web_state/web_state.mm b/ios/web/web_state/web_state.mm
index d3ed3c7ba2fd5d6705356f02d186f3df3da33395..084d9a620f439ab8e918e49bb128115822efb825 100644
--- a/ios/web/web_state/web_state.mm
+++ b/ios/web/web_state/web_state.mm
@@ -7,7 +7,12 @@
 namespace web {
 
 WebState::CreateParams::CreateParams(web::BrowserState* browser_state)
-    : browser_state(browser_state) {}
+    : CreateParams(browser_state, nil) {}
+
+WebState::CreateParams::CreateParams(
+    web::BrowserState* browser_state,
+    CRWNavigationManagerSerialization* serialization)
+    : browser_state(browser_state), serialization([serialization retain]) {}
 
 WebState::CreateParams::~CreateParams() {}