chrome: Update expectations with same-site BFCache enabled (fixes issue #3301)

With same-site BFCache enabled every navigation can now potentially be served
via the BFCache. To support this internally a new top-level RenderFrame object
may be created for each new navigation. As a result, OnBrowserCreated may now
be called multiple times with the same browser ID in a given renderer process
(a behavior previously only seen with cross-site navigations and different
renderer processes).

BFCache navigations do not trigger the same Chromium notifications as a normal
load. To avoid breaking CEF API usage expectations we now synthetically
generate the load-related callbacks that would otherwise be missing
(OnLoadingStateChange with isLoading=true, OnLoadStart, OnLoadEnd). The
|httpStatusCode| argument to OnLoadEnd will be 0 in this case.

To test:
- Run `FrameHandlerTest.*:MessageRouterTest.*:NavigationTest.*`
- Run `NavigationTest.LoadSameOriginLoadURL` for OnBrowserCreated behavior.
- Run `NavigationTest.History` for load-related callback behavior.

libcef/browser/browser_contents_delegate.cc

@@ -421,6 +421,10 @@ void CefBrowserContentsDelegate::DidFinishNavigation(
     // history state).
     if (!navigation_handle->IsSameDocument()) {
       OnLoadStart(frame.get(), navigation_handle->GetPageTransition());
+      if (navigation_handle->IsServedFromBackForwardCache()) {
+        // We won't get an OnLoadEnd notification from anywhere else.
+        OnLoadEnd(frame.get(), navigation_handle->GetURL(), 0);
+      }
     }
 
     if (is_main_frame) {