Update view manager to support content handling.

mojo/services/view_manager/view_manager_service_impl.cc

Index: mojo/services/view_manager/view_manager_service_impl.cc
diff --git a/mojo/services/view_manager/view_manager_service_impl.cc b/mojo/services/view_manager/view_manager_service_impl.cc
index 2311b74e7f7e78e911e3f4a361f577e5556b8bca..4938cb461210ddd8823dc9486f499bb494d0efe8 100644
--- a/mojo/services/view_manager/view_manager_service_impl.cc
+++ b/mojo/services/view_manager/view_manager_service_impl.cc
@@ -464,33 +464,25 @@ void ViewManagerServiceImpl::Embed(
     return;
   }
   const Node* node = GetNode(NodeIdFromTransportId(transport_view_id));
-  bool success = node && access_policy_->CanEmbed(node);
-  if (success) {
-    // Only allow a node to be the root for one connection.
-    const NodeId node_id(NodeIdFromTransportId(transport_view_id));
-    ViewManagerServiceImpl* connection_by_url =
-        root_node_manager_->GetConnectionByCreator(id_, url.To<std::string>());
-    ViewManagerServiceImpl* connection_with_node_as_root =
-        root_node_manager_->GetConnectionWithRoot(node_id);
-    if ((connection_by_url != connection_with_node_as_root ||
-         (!connection_by_url && !connection_with_node_as_root)) &&
-        (!connection_by_url || !connection_by_url->HasRoot(node_id))) {
-      RootNodeManager::ScopedChange change(this, root_node_manager_, true);
-      RemoveChildrenAsPartOfEmbed(node_id);
-      // Never message the originating connection.
-      root_node_manager_->OnConnectionMessagedClient(id_);
-      if (connection_with_node_as_root)
-        connection_with_node_as_root->RemoveRoot(node_id);
-      if (connection_by_url) {
-        connection_by_url->AddRoot(node_id, spir.Pass());
-      } else {
-        root_node_manager_->Embed(id_, url, transport_view_id, spir.Pass());
-      }
-    } else {
-      success = false;
-    }
+  if (!node && access_policy_->CanEmbed(node)) {
+    callback.Run(false);
+    return;
   }
-  callback.Run(success);
+
+  // Only allow a node to be the root for one connection.
+  const NodeId node_id(NodeIdFromTransportId(transport_view_id));
+  ViewManagerServiceImpl* existing_owner =
+      root_node_manager_->GetConnectionWithRoot(node_id);
+
+  RootNodeManager::ScopedChange change(this, root_node_manager_, true);
+  if (existing_owner) {
+    RemoveChildrenAsPartOfEmbed(node_id);
+    // Never message the originating connection.
+    root_node_manager_->OnConnectionMessagedClient(id_);
+    existing_owner->RemoveRoot(node_id);
+  }
+  root_node_manager_->Embed(id_, url, transport_view_id, spir.Pass());
+  callback.Run(true);
 }
 
 void ViewManagerServiceImpl::DispatchOnViewInputEvent(Id transport_view_id,