PlzNavigate: Add a browser test for basic navigations

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 f24982617bb4e1aee439ff23e38f355157fc35a3..daa7ea393b91f7538b6fa888b1695826eebaadfc 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -4381,6 +4381,7 @@ void RenderFrameImpl::BeginNavigation(blink::WebURLRequest* request) {
   // TODO(clamy): Same-document navigations should not be sent back to the
   // browser.
   // TODO(clamy): Data urls should not be sent back to the browser either.
+  Send(new FrameHostMsg_DidStartLoading(routing_id_, true));
   Send(new FrameHostMsg_BeginNavigation(routing_id_,
                                         MakeBeginNavigationParams(request),
                                         MakeCommonNavigationParams(request)));