Added minimal documentation to the KeyboardEvent class.

tools/dom/templates/html/dart2js/impl_KeyboardEvent.darttemplate

Index: tools/dom/templates/html/dart2js/impl_KeyboardEvent.darttemplate
diff --git a/tools/dom/templates/html/dart2js/impl_KeyboardEvent.darttemplate b/tools/dom/templates/html/dart2js/impl_KeyboardEvent.darttemplate
index 7c4b25ae14902ac86dc93f3945f52028214a035a..cea51332a80569b0c94099c574abfa52218e7a55 100644
--- a/tools/dom/templates/html/dart2js/impl_KeyboardEvent.darttemplate
+++ b/tools/dom/templates/html/dart2js/impl_KeyboardEvent.darttemplate
@@ -3,6 +3,15 @@
 // BSD-style license that can be found in the LICENSE file.
 
 
+/**
+ * An event that describes user interaction with the keyboard.
+ *
+ * The [type] of the event identifies what kind of interaction occurred.
+ *
+ * See also:
+ *
+ * * [KeyboardEvent](https://developer.mozilla.org/en/DOM/KeyboardEvent) at MDN.
+ */
 $(ANNOTATIONS)class $CLASSNAME$EXTENDS$IMPLEMENTS$NATIVESPEC {
 
   factory $CLASSNAME(String type,