Support redirectUrl at onHeadersReceived in WebRequest / DWR API

chrome/common/extensions/docs/templates/intros/declarativeWebRequest.html

 <h2 id="manifest">Manifest</h2>
 
 <p>
 You must declare the "declarativeWebRequest" permission in the
 <a href="manifest.html">extension manifest</a> to use this API,
 along with <a href="declare_permissions.html">host permissions</a>.
 </p>
 
 <pre data-filename="manifest.json">
 {
@@ skipping 162 matching lines @@
     <th>onHeadersReceived
     <th>onAuthRequired
   </tr>
   <tr><td>AddRequestCookie<td><td>✓<td><td>
   <tr><td>AddResponseCookie<td><td><td>✓<td>
   <tr><td>AddResponseHeader<td><td><td>✓<td>
   <tr><td>CancelRequest<td>✓<td>✓<td>✓<td>✓
   <tr><td>EditRequestCookie<td><td>✓<td><td>
   <tr><td>EditResponseCookie<td><td><td>✓<td>
   <tr><td>IgnoreRules<td>✓<td>✓<td>✓<td>✓
-  <tr><td>RedirectByRegEx<td>✓<td><td><td>
-  <tr><td>RedirectRequest<td>✓<td><td><td>
-  <tr><td>RedirectToEmptyDocument<td>✓<td><td><td>
-  <tr><td>RedirectToTransparentImage<td>✓<td><td><td>
+  <tr><td>RedirectByRegEx<td>✓<td><td>✓<td>
+  <tr><td>RedirectRequest<td>✓<td><td>✓<td>
+  <tr><td>RedirectToEmptyDocument<td>✓<td><td>✓<td>
+  <tr><td>RedirectToTransparentImage<td>✓<td><td>✓<td>
   <tr><td>RemoveRequestCookie<td><td>✓<td><td>
   <tr><td>RemoveRequestHeader<td><td>✓<td><td>
   <tr><td>RemoveResponseCookie<td><td><td>✓<td>
   <tr><td>RemoveResponseHeader<td><td><td>✓<td>
   <tr><td>SendMessageToExtension<td>✓<td>✓<td>✓<td>✓
   <tr><td>SetRequestHeader<td><td>✓<td><td>
 </table>
 </p>
 
 <p>
 <strong>Note:</strong> Applicable stages can be further constrained by using the
 "stages" attribute.
 </p>
 <p>
+<strong>Note:</strong> If a redirect action is declared at the onHeadersReceived
+stage, then POST requests will be redirected using the GET method. In other cases

[battre, 2014/03/25 00:47:30]

nit: 80 characters

[robwu, 2014/03/25 10:08:14]

Done.

+the HTTP method is preserved.

[battre, 2014/03/25 00:47:30]

Why is this?

[robwu, 2014/03/25 10:08:14]

onBeforeRequest = 307 redirect, which doesn't change the HTTP method.
onHeadersReceived = 302 redirect, which changes the HTTP method if the original
request was a POST request. I have changed the note to make this difference more
obvious.

+</p>
+<p>
 <strong>Example:</strong> It is possible to combine a
 <code>new chrome.declarativeWebRequest.RequestMatcher({contentType: ["image/jpeg"]})</code>
 condition with a <code>new chrome.declarativeWebRequest.CancelRequest()</code>
 action because both of them can be evaluated in the onHeadersReceived stage.
 It is, however, impossible to combine the request matcher with a
-<code>new chrome.declarativeWebRequest.RedirectToTransparentImage()</code>
-because redirects cannot be executed any more by the time the content
-type has been determined.
+<code>new chrome.declarativeWebRequest.SetRequestHeader()</code>
+because request headers cannot be set any more by the time the content type has been terminated.
 </p>
 
 <h2 id="precedences">Using priorities to override rules</h2>
 
 <p>
 Rules can be associated with priorities as described in the
 <a href="events.html#declarative">Events API</a>. This mechanism can be used
 to express exceptions. The following example will block all requests to
 images named "evil.jpg" except on the server "myserver.com".
 </p>
@@ skipping 23 matching lines @@
 chrome.declarativeWebRequest.onRequest.addRules([rule1, rule2]);
 </pre>
 
 <p>
 It is important to recognize that the <code>IgnoreRules</code> action is not
 persisted across <a href="#evaluation">request stages</a>. All conditions of
 all rules are evaluated at each stage of a web request. If an
 <code>IgnoreRules</code> action is executed, it applies only to other actions
 that are executed for the same web request in the same stage.
 </p>