OOPIF: Remove the FrameTreeNode when a RemoteFrame is detached.

content/browser/frame_host/frame_tree_node.cc

Index: content/browser/frame_host/frame_tree_node.cc
diff --git a/content/browser/frame_host/frame_tree_node.cc b/content/browser/frame_host/frame_tree_node.cc
index 7df1291a9f4cb8e0757e34f9e10498bfe865a121..955a08f003b8fb866aac9acaf5485acf6f38892e 100644
--- a/content/browser/frame_host/frame_tree_node.cc
+++ b/content/browser/frame_host/frame_tree_node.cc
@@ -169,4 +169,14 @@ bool FrameTreeNode::CommitPendingSandboxFlags() {
   return did_change_flags;
 }
 
+bool FrameTreeNode::HasAncestorFrom(SiteInstance* site_instance) const {
+  FrameTreeNode* parent_node = parent();
+  while (parent_node) {
+    if (parent_node->current_frame_host()->GetSiteInstance() == site_instance)
+      return true;
+    parent_node = parent_node->parent();
+  }
+  return false;
+}
+
 }  // namespace content