Implement ShadowRoot.delegatesFocus 4/4 (match CSS :focus for shadow host)

Source/core/dom/ContainerNode.cpp

Index: Source/core/dom/ContainerNode.cpp
diff --git a/Source/core/dom/ContainerNode.cpp b/Source/core/dom/ContainerNode.cpp
index f399213a53970bcd7f8a6b467d8ce43cac065ba5..efb14bfc14aaf4f9c1af11b9c1137f850642c6b9 100644
--- a/Source/core/dom/ContainerNode.cpp
+++ b/Source/core/dom/ContainerNode.cpp
@@ -1084,6 +1084,20 @@ void ContainerNode::focusStateChanged()
 
 void ContainerNode::setFocus(bool received)
 {
+    // Recurse up the shadow trees to mark shadow hosts if it matches :focus.

[hayato, 2015/06/12 04:37:57]

Could you add a layout test which involves a dom mutation?

If a focused element is moved to somewhere, the focus state of each nodes are
set (or unset) correctly?

[kochi, 2015/06/12 07:34:17]

Added 'focus-with-dom-mutation.html' layout test which tests :focus
state is properly cleared when focused element is moved out of shadow tree.

+    if (isInShadowTree() && shadowHost()->shadowRoot())

[hayato, 2015/06/12 04:37:57]

Not intuitive to me. Is this checking that `this` is in an author shadow tree or
not?

[kochi, 2015/06/12 07:34:17]

Yes, it's author shadow only.
Updated the comment and moved the TODO comment below (line 1093) here.

+        shadowHost()->setFocus(received);
+
+    // If this is an author shadow host and indirectly focused (has focused element within
+    // its shadow root), update focus.
+    // TODO(kochi): Handle UA shadow which marks multiple nodes as focused such as
+    // <input type="date"> the same way as author shadow.
+    if (document().focusedElement() && document().focusedElement() != this) {
+        Element* host = toElement(this);

[hayato, 2015/06/12 04:37:57]

1. Looks isElementNode() is used in L1112.
 `this` is always Element here?

2. `host` looks confusing name to me since `this` is not always a shadow host,
at least until 1098.

[kochi, 2015/06/12 07:34:17]

1. Good catch.  I guess no one is calling setFocus() on Node or ContainerNode,
but adding isElementNode() here looks correct to me.  The same bug existed for
the old tabStop implementation.

2. replaced toElement() for both occurrences.

+        if (host->shadowRoot())
+            received = received && host->shadowRoot()->delegatesFocus();
+    }
+
     if (focused() == received)
         return;