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 d28c0f4b6e3516e18495da49345c426bce1be7f9..509e577b7a809d4f94b07176284af11b8b7ef499 100644
--- a/content/renderer/render_frame_impl.cc
+++ b/content/renderer/render_frame_impl.cc
@@ -3449,19 +3449,19 @@ void RenderFrameImpl::didCreateDataSource(blink::WebLocalFrame* frame,
           content_initiated));
 }
 
-void RenderFrameImpl::didStartProvisionalLoad(blink::WebLocalFrame* frame) {
+void RenderFrameImpl::didStartProvisionalLoad(
+    blink::WebLocalFrame* frame,
+    blink::WebDataSource* data_source) {
   DCHECK_EQ(frame_, frame);
-  WebDataSource* ds = frame->provisionalDataSource();
-
   // In fast/loader/stop-provisional-loads.html, we abort the load before this
   // callback is invoked.
-  if (!ds)
+  if (!data_source)
     return;
 
   TRACE_EVENT2("navigation,benchmark,rail",
                "RenderFrameImpl::didStartProvisionalLoad", "id", routing_id_,
-               "url", ds->getRequest().url().string().utf8());
-  DocumentState* document_state = DocumentState::FromDataSource(ds);
+               "url", data_source->getRequest().url().string().utf8());
+  DocumentState* document_state = DocumentState::FromDataSource(data_source);
   NavigationStateImpl* navigation_state = static_cast<NavigationStateImpl*>(
       document_state->navigation_state());
   bool is_top_most = !frame->parent();
@@ -3469,7 +3469,7 @@ void RenderFrameImpl::didStartProvisionalLoad(blink::WebLocalFrame* frame) {
     render_view_->set_navigation_gesture(
         WebUserGestureIndicator::isProcessingUserGesture() ?
             NavigationGestureUser : NavigationGestureAuto);
-  } else if (ds->replacesCurrentHistoryItem()) {
+  } else if (data_source->replacesCurrentHistoryItem()) {
     // Subframe navigations that don't add session history items must be
     // marked with AUTO_SUBFRAME. See also didFailProvisionalLoad for how we
     // handle loading of error pages.
@@ -3483,10 +3483,10 @@ void RenderFrameImpl::didStartProvisionalLoad(blink::WebLocalFrame* frame) {
   for (auto& observer : render_view_->observers())
     observer.DidStartProvisionalLoad(frame);
   for (auto& observer : observers_)
-    observer.DidStartProvisionalLoad();
+    observer.DidStartProvisionalLoad(data_source);
 
   Send(new FrameHostMsg_DidStartProvisionalLoad(
-      routing_id_, ds->getRequest().url(), navigation_start));
+      routing_id_, data_source->getRequest().url(), navigation_start));
 }
 
 void RenderFrameImpl::didReceiveServerRedirectForProvisionalLoad(