Add support for switching frames with the webdriver API.

This moves webdriver_traits into msg to avoid a circular dependency.

components/msg/webdriver_msg.rs

@@ -0,0 +1,56 @@
+/* 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 rustc_serialize::json::{Json, ToJson};
+use constellation_msg::{PipelineId, SubpageId};
+
+use std::sync::mpsc::Sender;
+
+pub enum WebDriverScriptCommand {
+    ExecuteScript(String, Sender<WebDriverJSResult>),
+    ExecuteAsyncScript(String, Sender<WebDriverJSResult>),
+    FindElementCSS(String, Sender<Result<Option<String>, ()>>),
+    FindElementsCSS(String, Sender<Result<Vec<String>, ()>>),
+    GetActiveElement(Sender<Option<String>>),
+    GetElementTagName(String, Sender<Result<String, ()>>),
+    GetElementText(String, Sender<Result<String, ()>>),
+    GetFrameId(WebDriverFrameId, Sender<Result<Option<(PipelineId, SubpageId)>, ()>>),
+    GetTitle(Sender<String>)
+}
+
+pub enum WebDriverJSValue {
+    Undefined,
+    Null,
+    Boolean(bool),
+    Number(f64),
+    String(String),
+    // TODO: Object and WebElement
+}
+
+pub enum WebDriverJSError {
+    Timeout,
+    UnknownType
+}
+
+pub type WebDriverJSResult = Result<WebDriverJSValue, WebDriverJSError>;
+
+pub enum WebDriverFrameId {
+    Short(u16),
+    Element(String),
+    Parent
+}
+
+impl ToJson for WebDriverJSValue {
+    fn to_json(&self) -> Json {
+        match *self {
+            WebDriverJSValue::Undefined => Json::Null,
+            WebDriverJSValue::Null => Json::Null,
+            WebDriverJSValue::Boolean(ref x) => x.to_json(),
+            WebDriverJSValue::Number(ref x) => x.to_json(),
+            WebDriverJSValue::String(ref x) => x.to_json()
+        }
+    }
+}
+
+pub struct LoadComplete;