Implement ProcessingInstruction DOM interface

Spec:
http://dom.spec.whatwg.org/#interface-processinginstruction

Closes #1619.

src/components/script/dom/processinginstruction.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::ProcessingInstructionBinding;
+use dom::bindings::utils::DOMString;
+use dom::characterdata::CharacterData;
+use dom::document::AbstractDocument;
+use dom::node::{AbstractNode, Node, ProcessingInstructionNodeTypeId};
+
+/// An HTML processing instruction node.
+pub struct ProcessingInstruction {
+    // FIXME: s/element/characterdata/ https://github.com/mozilla/servo/issues/1594
+    element: CharacterData,
+    target: DOMString,
+}
+
+impl ProcessingInstruction {
+    pub fn new_inherited(target: DOMString, data: DOMString, document: AbstractDocument) -> ProcessingInstruction {
+        ProcessingInstruction {
+            element: CharacterData::new_inherited(ProcessingInstructionNodeTypeId, data, document),
+            target: target
+        }
+    }
+
+    pub fn new(target: DOMString, data: DOMString, document: AbstractDocument) -> AbstractNode {
+        let node = ProcessingInstruction::new_inherited(target, data, document);
+        Node::reflect_node(@mut node, document, ProcessingInstructionBinding::Wrap)
+    }
+}
+
+impl ProcessingInstruction {
+    pub fn Target(&self) -> DOMString {
+        self.target.clone()
+    }
+}