Expose whether a frame is focused to the browser process

content/browser/frame_host/frame_tree_node.cc

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "content/browser/frame_host/frame_tree_node.h"
 
 #include <queue>
 
 #include "base/command_line.h"
 #include "base/stl_util.h"
@@ skipping 80 matching lines @@
   // The RenderFrame no longer exists and will need to be created again.
   current_frame_host()->SetRenderFrameCreated(false);
 
   // The children may not have been cleared if a cross-process navigation
   // commits before the old process cleans everything up.  Make sure the child
   // nodes get deleted before swapping to a new process.
   ScopedVector<FrameTreeNode> old_children = children_.Pass();
   old_children.clear();  // May notify observers.
 }
 
+bool FrameTreeNode::IsDescendantOf(FrameTreeNode* other) const {
+  if (!other || !other->child_count())
+    return false;
+
+  for (FrameTreeNode* node = parent(); node; node = node->parent()) {
+    if (node == other)
+      return true;
+  }
+
+  return false;
+}
+
 }  // namespace content