Allow override of user agent depending on url.

content/renderer/render_frame_impl.cc

Index: content/renderer/render_frame_impl.cc
diff --git a/content/renderer/render_frame_impl.cc b/content/renderer/render_frame_impl.cc
index ca5cf55aa3761765972eae6c626116de02aeba1e..7ea9fa728cabedc513eba73c9cd468a6868bdeb9 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -3129,6 +3129,11 @@ bool RenderFrameImpl::willCheckAndDispatchMessageEvent(
 blink::WebString RenderFrameImpl::userAgentOverride(blink::WebLocalFrame* frame,
                                                     const blink::WebURL& url) {
   DCHECK(!frame_ || frame_ == frame);
+  std::string user_agent_override_for_url =
+      GetContentClient()->renderer()->GetUserAgentOverrideForURL(GURL(url));
+  if (!user_agent_override_for_url.empty())
+    return WebString::fromUTF8(user_agent_override_for_url);
+
   if (!render_view_->webview() || !render_view_->webview()->mainFrame() ||
       render_view_->renderer_preferences_.user_agent_override.empty()) {
     return blink::WebString();