Add DOMImplementation skeleton

Creates a DOMImplementation struct corresponding to DOMImplementation
WebIDL. Also implements a getter for Document::implementation.

Closes #1486.

src/components/script/dom/domimplementation.rs

@@ -0,0 +1,36 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * 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::DOMImplementationBinding;
+use dom::bindings::utils::{Reflector, Reflectable, reflect_dom_object};
+use dom::window::Window;
+
+pub struct DOMImplementation {
+    owner: @mut Window,
+    reflector_: Reflector
+}
+
+impl DOMImplementation {
+    pub fn new_inherited(owner: @mut Window) -> DOMImplementation {
+        DOMImplementation {
+            owner: owner,
+            reflector_: Reflector::new()
+        }
+    }
+
+    pub fn new(owner: @mut Window) -> @mut DOMImplementation {
+        reflect_dom_object(@mut DOMImplementation::new_inherited(owner), owner,
+                           DOMImplementationBinding::Wrap)
+    }
+}
+
+impl Reflectable for DOMImplementation {
+    fn reflector<'a>(&'a self) -> &'a Reflector {
+        &self.reflector_
+    }
+
+    fn mut_reflector<'a>(&'a mut self) -> &'a mut Reflector {
+        &mut self.reflector_
+    }
+}