Add "matchingTarget" function to Event, which is the Element that matched the CSS value selector.

tools/dom/templates/html/impl/impl_Event.darttemplate

Index: tools/dom/templates/html/impl/impl_Event.darttemplate
diff --git a/tools/dom/templates/html/impl/impl_Event.darttemplate b/tools/dom/templates/html/impl/impl_Event.darttemplate
index a3fc47f660dd5faa429cd19a30bde06f4fc51673..54ebb3e5138b8810364d7d9f39aeb86ab85225fa 100644
--- a/tools/dom/templates/html/impl/impl_Event.darttemplate
+++ b/tools/dom/templates/html/impl/impl_Event.darttemplate
@@ -34,6 +34,35 @@ $(ANNOTATIONS)$(CLASS_MODIFIERS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
     return e;
   }
 
-  $CLASSNAME._private();
+  /** 
+   * Caches the pointer to the element that matches CSS selector involved in
+   * the event.
+   */
+  Element _cachedMatchingTarget;

[blois, 2013/10/09 22:25:44]

Probably does not need to be cached- in most cases it's only called once.

Plus adding fields to native types in JS need more annotations I think.

[Emily Fortuna, 2013/10/09 22:39:18]

Removed

+  
+  /** The CSS selector involved with event delegation. */
+  String _selector;
+
+  /**
+   * A pointer to the element whose CSS selector matched within which an event
+   * was fired. If this Event was not associated with any Event delegation,
+   * then this value will be null.
+   */
+  Element matchingTarget() {

[blois, 2013/10/09 22:25:44]

Can this be a getter?

[Emily Fortuna, 2013/10/09 22:39:18]

Yeah, but it felt like a function was a little more appropriate since it does a
chunk of calculation beforehand. If you prefer I can switch it though.

[blois, 2013/10/09 23:12:57]

Yes plz! It just feels odd as a method when it's beside target and
currentTarget.

+    if (_cachedMatchingTarget == null) {
+      var currentTarget = this.currentTarget;
+      var target = this.target;
+      var matchedTarget;
+      while (matchedTarget == null && target != currentTarget && 
+          target != null) {
+        if (_selector != null && target.matches(_selector)) {

[blois, 2013/10/09 22:25:44]

Can there be an earlier out if _selector is null? Possibly even throw?

[Emily Fortuna, 2013/10/09 22:39:18]

added earlier out.

+          matchedTarget = target;
+        }
+        target = target.parent;
+      }
+      _cachedMatchingTarget = matchedTarget;
+    }
+    return _cachedMatchingTarget;
+  }
 $!MEMBERS
 }