1 files changed, 13 insertions, 0 deletions
diff --git a/content/browser/frame_host/frame_tree_node.cc b/content/browser/frame_host/frame_tree_node.cc
index 3db5b6c..b87af21 100644
--- a/content/browser/frame_host/frame_tree_node.cc
+++ b/content/browser/frame_host/frame_tree_node.cc
@@ -162,6 +162,19 @@ bool FrameTreeNode::IsDescendantOf(FrameTreeNode* other) const {
   return false;
 }
 
+FrameTreeNode* FrameTreeNode::PreviousSibling() const {
+  if (!parent_)
+    return nullptr;
+
+  for (size_t i = 0; i < parent_->child_count(); ++i) {
+    if (parent_->child_at(i) == this)
+      return (i == 0) ? nullptr : parent_->child_at(i - 1);
+  }
+
+  NOTREACHED() << "FrameTreeNode not found in its parent's children.";
+  return nullptr;
+}
+
 bool FrameTreeNode::IsLoading() const {
   RenderFrameHostImpl* current_frame_host =
       render_manager_.current_frame_host();