Move Execute Script to a promise based approach. Fixes w3c#381

This moves Execute Script to be Promise based and removes the
need for execute script async. The patch also updates the end
points to be like the Selenium JSONWP.

webdriver-spec.html

@@ -1259,16 +1259,10 @@ <h3>List of Endpoints</h3>
 
  <tr>
   <td>POST</td>
-  <td>/session/{<var>session id</var>}/execute/sync</td>
+  <td>/session/{<var>session id</var>}/execute</td>
   <td><a>Execute Script</a></td>
  </tr>
 
- <tr>
-  <td>POST</td>
-  <td>/session/{<var>session id</var>}/execute/async</td>
-  <td><a>Execute Async Script</a></td>
- </tr>
-
  <tr>
   <td>GET</td>
   <td>/session/{<var>session id</var>}/cookie</td>
@@ -5744,7 +5738,7 @@ <h3>Execute Script</h3>
  </tr>
  <tr>
   <td>POST</td>
-  <td>/session/{<var>session id</var>}/execute/sync</td>
+  <td>/session/{<var>session id</var>}/execute</td>
  </tr>
 </table>
 
@@ -5773,118 +5767,19 @@ <h3>Execute Script</h3>
  <li><p>Let <var>result</var> be the result of calling <a>execute a function body</a>,
   with arguments <var>body</var> and <var>arguments</var>.
 
- <li><p>Wait for <a>execute a function body</a> to return
-  or for <a>session script timeout</a> milliseconds to expire,
-  whichever happens sooner.
+ <li><p>Let <var>promise</var> be a new Promise.
 
- <li><p>If the previous step completed due to the <a>session script timeout</a> being reached,
-  return <a>error</a> with <a>error code</a> <a>script timeout</a>.
-
- <li><p>If <var>result</var> is an <a>error</a>, return result.
+ <li><p>Let <var>result</var> be the result of <a>execute a function body</a>.
+   If <var>result</var> is an <a>error</a> or if for <a>session script timeout</a>
+   milliseconds to expire,
+   reject <var>promise</var> else
+   resolve <var>promise</var> with <var>result</var>.
 
  <li><p>Otherwise let <var>value</var> be <var>result</var>’s data.
 
  <li><p>Return <a>success</a> with data <var>value</var>.
 </ol>
 </section> <!-- /Execute Script -->
-
-<section>
-<h3>Execute Async Script</h3>
-
-<table class="simple jsoncommand">
- <tr>
-  <th>HTTP Method</th>
-  <th>Path Template</th>
- </tr>
- <tr>
-  <td>POST</td>
-  <td>/session/{<var>session id</var>}/execute/async</td>
- </tr>
-</table>
-
-<p>The <dfn>Execute Async Script</dfn> <a>command</a>
- causes JavaScript to execute as an anonymous function.
- Unlike the <a>Execute Script</a> <a>command</a>,
- the result of the function is ignored.
- Instead an additional argument is provided as the final argument to the function.
- This is a function that, when called, returns its first argument as the response.
-
-<p>The <a>remote end steps</a> are:
-
-<ol>
- <li><p>If the <a>current browsing context</a> is <a>no longer open</a>,
-  return <a>error</a> with <a>error code</a> <a>no such window</a>.
-
- <li><p><a>Handle any user prompts</a>, and return its value if it is an <a>error</a>.
-
- <li><p>Let <var>script arguments</var> be the result
-  of <a>extracting the script arguments from a request</a>
-  with argument <var>parameters</var>.
-
- <li><p>If <var>script arguments</var> is an <a>error</a>,
-  return <var>script arguments</var>.
-
- <li><p>Let <var>body</var> and <var>arguments</var>
-  be <var>script arguments</var>’ data.
-
- <li><p class=issue>This next step might not quite set up all the right machinery.
-
-  <p>Let <var>webdriver callback result</var> be
-   a flag which can have three values:
-   <code>unset</code>, <code>expired</code>, or <code>set</code>,
-   with the <code>set</code> value having associated data.
-   Initially it is in the <code>unset</code> state.
-
- <li><p>Let <var>callback</var> be a <a>function</a>
-  whose <a>[[\Call]]</a> <a>internal method</a> runs
-  the <a>execute async script callback</a> algorithm
-  initialized with argument <var>webdriver callback result</var>.
-
- <li><p>Append <var>callback</var> to <var>arguments</var>.
-
- <li><p>Let <var>result</var> be the result
-  of <a>trying</a> to call <a>execute a function body</a>
-  with arguments <var>body</var> and <var>arguments</var>.
-
- <li><p>Wait for <var>webdriver callback result</var> to enter the <code>set</code> state,
-  or for <a>session script timeout</a> milliseconds to expire,
-  whichever happens sooner.
-
- <li><p>If the previous step completed due the <a>session script timeout</a> being reached,
-  set <var>webdriver callback result</var> to <code>expired</code>
-  and return <a>error</a> with <a>error code</a> <a>script timeout</a>.
-
- <li><p>Otherwise, let <var>result</var> be <var>webdriver callback result</var>’s data.
-
- <li><p>If <var>result</var> is an <a>error</a>, return <var>result</var>.
-
- <li><p>Let <var>value</var> be <var>result</var>’s data.
-
- <li><p>Return <a>success</a> with data <var>value</var>.
-</ol>
-
-<p>The <dfn>execute async script callback</dfn> algorithm
- is initialized with a single argument <var>webdriver callback state</var>.
- It defines a <a>function</a> with a single optional argument <var>result</var>.
- When this function is called, the following steps are run:
-
-<ol>
- <li><p>If <var>webdriver callback state</var> is not in the <code>unset</code> state,
-  return <code><a>undefined</a></code>.
-
-
- <li><p>If <var>result</var> is not present,
-  let <var>result</var> be <code>null</code>.
-
- <li><p>Let <var>json result</var> be a <a>JSON clone</a>
-  of <var>result</var>.
-
- <li><p>Set the <var>webdriver callback state</var>
-  to <code>set</code> with data <var>json result</var>.
-
- <li><p>Return <code><a>undefined</a></code>.
-</ol>
-</section> <!-- /Execute Async Script -->
 </section> <!-- /Executing Script -->
 </section> <!-- /Document Handling -->
 <section>