Pepper: Add a X-Requested-With header to URL requests done for Pepper plugins.

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index fd18ad12f38bd5c74efabbc9da61f111f82687f0..04b69b648e0c79f4c3e27488ee01b18b34951c1a 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -3669,25 +3669,37 @@ void RenderViewImpl::willSendRequest(WebFrame* frame,
 
   // The request's extra data may indicate that we should set a custom user
   // agent. This needs to be done here, after WebKit is through with setting the
-  // user agent on its own.
+  // user agent on its own. Similarly, it may indicate that we should set an
+  // X-Requested-With header. This must be done here to avoid breaking CORS
+  // checks.
   WebString custom_user_agent;
+  WebString requested_with;
   if (request.extraData()) {
     webkit_glue::WebURLRequestExtraDataImpl* old_extra_data =
         static_cast<webkit_glue::WebURLRequestExtraDataImpl*>(
             request.extraData());
-    custom_user_agent = old_extra_data->custom_user_agent();
 
+    custom_user_agent = old_extra_data->custom_user_agent();
     if (!custom_user_agent.isNull()) {
       if (custom_user_agent.isEmpty())
         request.clearHTTPHeaderField("User-Agent");
       else
         request.setHTTPHeaderField("User-Agent", custom_user_agent);
     }
+
+    requested_with = old_extra_data->requested_with();
+    if (!requested_with.isNull()) {
+      if (requested_with.isEmpty())
+        request.clearHTTPHeaderField("X-Requested-With");
+      else
+        request.setHTTPHeaderField("X-Requested-With", requested_with);
+    }
   }
 
   request.setExtraData(
       new RequestExtraData(referrer_policy,
                            custom_user_agent,
+                           requested_with,
                            (frame == top_frame),
                            frame->identifier(),
                            frame->parent() == top_frame,