Add mount sources for a MountNode (inode)

native_client_sdk/src/libraries/nacl_mounts/mount_node.cc

Index: native_client_sdk/src/libraries/nacl_mounts/mount_node.cc
===================================================================
--- native_client_sdk/src/libraries/nacl_mounts/mount_node.cc	(revision 131457)
+++ native_client_sdk/src/libraries/nacl_mounts/mount_node.cc	(working copy)
@@ -30,9 +30,9 @@
   return true;
 }
 
-void MountNode::Destroy() {
+int MountNode::Close() {
   FSync();
-  mount_->FreeNode(this);
+  return 0;
 }
 
 int MountNode::FSync() {
@@ -113,6 +113,11 @@
   return NULL;
 }
 
+int MountNode::ChildCount() {
+  errno = ENOTDIR;
+  return -1;
+}
+
 void MountNode::Link() {
   Acquire();
   stat_.st_nlink++;