Fix keyboard focus for OOPIF-<webview>.

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 9977976aaba40eb87ec1c970367ba9b3f85a4053..cf9f2e647bfde775d9ecfc23e46497105e172a24 100644
--- a/content/browser/frame_host/frame_tree.cc
+++ b/content/browser/frame_host/frame_tree.cc
@@ -251,6 +251,17 @@ void FrameTree::SetFocusedFrame(FrameTreeNode* node, SiteInstance* source) {
   if (node == GetFocusedFrame())
     return;
 
+  if (node == nullptr) {
+    if (GetFocusedFrame())
+      GetFocusedFrame()->current_frame_host()->ClearFocusedFrame();
+    focused_frame_tree_node_id_ = FrameTreeNode::kFrameTreeNodeInvalidId;
+
+    // TODO(avallee): https://crbug.com/610795 This line is not sufficient to
+    // make the test pass. There seems to be no focus change events generated.
+    root()->current_frame_host()->UpdateAXTreeData();
+    return;
+  }
+
   std::set<SiteInstance*> frame_tree_site_instances =
       CollectSiteInstances(this);