Resetting FrameTreeNode must remove child FrameTreeNodes from global map.

content/browser/frame_host/frame_tree.cc

Index: content/browser/frame_host/frame_tree.cc
diff --git a/content/browser/frame_host/frame_tree.cc b/content/browser/frame_host/frame_tree.cc
index 183ccde1a7e2445923bdffa245ec137a8fd51aa0..25cc7f97279a2c6bf64c5e5ca2680f3bb0f4b091 100644
--- a/content/browser/frame_host/frame_tree.cc
+++ b/content/browser/frame_host/frame_tree.cc
@@ -182,6 +182,10 @@ void FrameTree::RemoveFrame(FrameTreeNode* child) {
   parent->RemoveChild(child);
 }
 
+void FrameTree::RemoveNodeFromMap(int64 frame_tree_node_id) {
+  g_frame_tree_node_id_map.Get().erase(frame_tree_node_id);
+}
+
 void FrameTree::CreateProxiesForSiteInstance(
     FrameTreeNode* source,
     SiteInstance* site_instance) {