Require a process ID when looking up RFHs by FrameTreeNode ID.

content/browser/frame_host/navigation_handle_impl.cc

Index: content/browser/frame_host/navigation_handle_impl.cc
diff --git a/content/browser/frame_host/navigation_handle_impl.cc b/content/browser/frame_host/navigation_handle_impl.cc
index 37f1c0c581746f799c9578ace7b1a76f98236dcb..c4524a8a7c3e821dcff3c9d33ec625071afdc5bc 100644
--- a/content/browser/frame_host/navigation_handle_impl.cc
+++ b/content/browser/frame_host/navigation_handle_impl.cc
@@ -230,11 +230,11 @@ int NavigationHandleImpl::GetFrameTreeNodeId() {
   return frame_tree_node_->frame_tree_node_id();
 }
 
-int NavigationHandleImpl::GetParentFrameTreeNodeId() {
+RenderFrameHostImpl* NavigationHandleImpl::GetParentFrame() {
   if (frame_tree_node_->IsMainFrame())
-    return FrameTreeNode::kFrameTreeNodeInvalidId;
+    return nullptr;
 
-  return frame_tree_node_->parent()->frame_tree_node_id();
+  return frame_tree_node_->parent()->current_frame_host();
 }
 
 const base::TimeTicks& NavigationHandleImpl::NavigationStart() {