Moved NavigationManagerImpl serialization out of CRWSessionController.

ios/web/navigation/navigation_manager_impl.mm

Index: ios/web/navigation/navigation_manager_impl.mm
diff --git a/ios/web/navigation/navigation_manager_impl.mm b/ios/web/navigation/navigation_manager_impl.mm
index 4b18be88345415b1d138cf83c4b074caa5826a6d..9789ce3473bda7a8ddde25d4c6ecf57d614d3c82 100644
--- a/ios/web/navigation/navigation_manager_impl.mm
+++ b/ios/web/navigation/navigation_manager_impl.mm
@@ -34,13 +34,21 @@ bool AreURLsInPageNavigation(const GURL& existing_url, const GURL& new_url) {
 
 namespace web {
 
-NavigationManagerImpl::NavigationManagerImpl(
-    NavigationManagerDelegate* delegate,
-    BrowserState* browser_state)
-    : delegate_(delegate),
-      browser_state_(browser_state),
-      facade_delegate_(nullptr) {
-  DCHECK(browser_state_);
+NavigationManagerImpl::NavigationManagerImpl()
+    : delegate_(nullptr), browser_state_(nullptr), facade_delegate_(nullptr) {}
+
+NavigationManagerImpl::NavigationManagerImpl(const NavigationManagerImpl& other)
+    : delegate_(nullptr),
+      browser_state_(other.browser_state_),
+      session_controller_([other.session_controller_ copy]),
+      facade_delegate_(nullptr) {}
+
+void NavigationManagerImpl::SetDelegate(NavigationManagerDelegate* delegate) {
+  delegate_ = delegate;
+}
+
+void NavigationManagerImpl::SetBrowserState(BrowserState* browser_state) {
+  browser_state_ = browser_state;
 }
 
 NavigationManagerImpl::~NavigationManagerImpl() {
@@ -81,6 +89,11 @@ void NavigationManagerImpl::ReplaceSessionHistory(
                  browserState:browser_state_] autorelease]);
 }
 
+scoped_ptr<NavigationManagerImpl> NavigationManagerImpl::CopyForSerialization()
+    const {
+  return scoped_ptr<NavigationManagerImpl>(new NavigationManagerImpl(*this));
+}
+
 void NavigationManagerImpl::SetFacadeDelegate(
     NavigationManagerFacadeDelegate* facade_delegate) {
   facade_delegate_ = facade_delegate;