PlzNavigate: Invoke didStartProvisionalLoad() when the renderer initiates a navigation in startLoad(

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 f30efe82ac6b9e289c5545f1ad70f8593fcd306a..e576a1463ca2018a789c41c321b80f5f6980fedc 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -6181,6 +6181,8 @@ void RenderFrameImpl::BeginNavigation(const NavigationPolicyInfo& info) {
   CHECK(IsBrowserSideNavigationEnabled());
   browser_side_navigation_pending_ = true;
 
+  didStartProvisionalLoad(frame_);
+
   // Note: At this stage, the goal is to apply all the modifications the
   // renderer wants to make to the request, and then send it to the browser, so
   // that the actual network request can be started. Ideally, all such