Add DateTime string attribute to Time

Also handle datetime content attribute when attribute is absent.

Rephrase terms used in the test: dateTime IDL property, datetime
attribute and datetime content attribute.

Remove failure expectations for time element.

components/script/dom/htmltimeelement.rs

@@ -2,23 +2,27 @@
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
+use dom::bindings::codegen::Bindings::ElementBinding::ElementBinding::ElementMethods;
 use dom::bindings::codegen::Bindings::HTMLTimeElementBinding;
+use dom::bindings::codegen::Bindings::HTMLTimeElementBinding::HTMLTimeElementMethods;
+use dom::bindings::inheritance::Castable;
 use dom::bindings::js::Root;
 use dom::bindings::str::DOMString;
 use dom::document::Document;
+use dom::element::Element;
 use dom::htmlelement::HTMLElement;
 use dom::node::Node;
 use html5ever_atoms::LocalName;
 
 #[dom_struct]
 pub struct HTMLTimeElement {
-    htmlelement: HTMLElement
+    htmlelement: HTMLElement,
 }
 
 impl HTMLTimeElement {
     fn new_inherited(local_name: LocalName, prefix: Option<DOMString>, document: &Document) -> HTMLTimeElement {
         HTMLTimeElement {
-            htmlelement: HTMLElement::new_inherited(local_name, prefix, document)
+            htmlelement: HTMLElement::new_inherited(local_name, prefix, document),
         }
     }
 
@@ -31,3 +35,22 @@ impl HTMLTimeElement {
                            HTMLTimeElementBinding::Wrap)
     }
 }
+
+impl HTMLTimeElementMethods for HTMLTimeElement {
+    // https://html.spec.whatwg.org/multipage/#dom-time-datetime
+    //make_getter!(DateTime, "datetime");
+    fn DateTime(&self) -> DOMString {
+        let element = self.upcast::<Element>();
+        if element.has_attribute(&local_name!("datetime")) {
+            return element.get_string_attribute(&local_name!("datetime"))
+        } else {
+            match element.GetInnerHTML() {
+                Ok(x) => x,
+                _ => DOMString::new(),
+            }
+        }
+    }
+
+    // https://html.spec.whatwg.org/multipage/#dom-time-datetime
+    make_setter!(SetDateTime, "datetime");
+}