Fixes bug where IViewManagerClient could be messaged unnecessarily

mojo/services/view_manager/root_node_manager.h

Index: mojo/services/view_manager/root_node_manager.h
diff --git a/mojo/services/view_manager/root_node_manager.h b/mojo/services/view_manager/root_node_manager.h
index 204f1586b9226d0e272cf52f8d5f42b75f021c33..1598e0dc35cb35ba8a2a536d2745e2d6fbeefe10 100644
--- a/mojo/services/view_manager/root_node_manager.h
+++ b/mojo/services/view_manager/root_node_manager.h
@@ -48,9 +48,28 @@ class MOJO_VIEW_MANAGER_EXPORT RootNodeManager : public NodeDelegate {
                  bool is_delete_node);
     ~ScopedChange();
 
+    TransportConnectionId connection_id() const { return connection_id_; }
+    ChangeType change_type() const { return change_type_; }
+    bool is_delete_node() const { return is_delete_node_; }
+
+    // Marks the connection with the specified id as having seen a message.
+    void MarkConnectionAsMessaged(TransportConnectionId connection_id) {
+      message_ids_.insert(connection_id);
+    }
+
+    // Returns true if MarkConnectionAsMessaged(connection_id) was invoked.
+    bool DidMessageConnection(TransportConnectionId connection_id) const {
+      return message_ids_.count(connection_id) > 0;
+    }
+
    private:
     RootNodeManager* root_;
+    const TransportConnectionId connection_id_;
     const ChangeType change_type_;
+    const bool is_delete_node_;
+
+    // See description of MarkConnectionAsMessaged/DidMessageConnection.
+    std::set<TransportConnectionId> message_ids_;
 
     DISALLOW_COPY_AND_ASSIGN(ScopedChange);
   };
@@ -88,9 +107,17 @@ class MOJO_VIEW_MANAGER_EXPORT RootNodeManager : public NodeDelegate {
 
   Node* root() { return &root_; }
 
-  bool IsProcessingChange() const { return change_source_ != 0; }
+  bool IsProcessingChange() const { return current_change_ != NULL; }
+
+  bool is_processing_delete_node() const {
+    return current_change_ && current_change_->is_delete_node(); }
 
-  bool is_processing_delete_node() const { return is_processing_delete_node_; }
+  // Invoked when a connection messages a client about the change. This is used
+  // to avoid sending ServerChangeIdAdvanced() unnecessarily.
+  void OnConnectionMessagedClient(TransportConnectionId id);
+
+  // Returns true if OnConnectionMessagedClient() was invoked for id.
+  bool DidConnectionMessageClient(TransportConnectionId id) const;
 
   // These functions trivially delegate to all ViewManagerConnections, which in
   // term notify their clients.
@@ -115,20 +142,20 @@ class MOJO_VIEW_MANAGER_EXPORT RootNodeManager : public NodeDelegate {
 
   typedef std::map<TransportConnectionId, ViewManagerConnection*> ConnectionMap;
 
-  // Invoked when a particular connection is about to make a change.
-  // Subsequently followed by FinishChange() once the change is done.
+  // Invoked when a connection is about to make a change.  Subsequently followed
+  // by FinishChange() once the change is done.
   //
   // Changes should never nest, meaning each PrepareForChange() must be
   // balanced with a call to FinishChange() with no PrepareForChange()
   // in between.
-  void PrepareForChange(ViewManagerConnection* connection, bool is_delete_node);
+  void PrepareForChange(ScopedChange* change);
 
   // Balances a call to PrepareForChange().
-  void FinishChange(ChangeType change_type);
+  void FinishChange();
 
   // Returns true if the specified connection originated the current change.
   bool IsChangeSource(TransportConnectionId connection_id) const {
-    return connection_id == change_source_;
+    return current_change_ && current_change_->connection_id() == connection_id;
   }
 
   // Implementation of the two connect variants.
@@ -155,12 +182,6 @@ class MOJO_VIEW_MANAGER_EXPORT RootNodeManager : public NodeDelegate {
   // Set of ViewManagerConnections.
   ConnectionMap connection_map_;
 
-  // If non-zero we're processing a change from this client.
-  TransportConnectionId change_source_;
-
-  // True if we're processing a DeleteNode request.
-  bool is_processing_delete_node_;
-
   RootViewManager root_view_manager_;
 
   // Root node.
@@ -170,6 +191,10 @@ class MOJO_VIEW_MANAGER_EXPORT RootNodeManager : public NodeDelegate {
   // explicitly destroyed.
   std::set<ViewManagerConnection*> connections_created_by_connect_;
 
+  // If non-null we're processing a change. The ScopedChange is not owned by us
+  // (it's created on the stack by ViewManagerConnection).
+  ScopedChange* current_change_;
+
   DISALLOW_COPY_AND_ASSIGN(RootNodeManager);
 };