PlzNavigate: make content unit tests work with browser side navigation

content/browser/frame_host/render_frame_host_impl.h

Index: content/browser/frame_host/render_frame_host_impl.h
diff --git a/content/browser/frame_host/render_frame_host_impl.h b/content/browser/frame_host/render_frame_host_impl.h
index 7b40b9da8db2ce29171cdd0deb5eb32f3fcfcf0d..9ea8c478ce21804a9bfec8bb67968cb6b9ae105f 100644
--- a/content/browser/frame_host/render_frame_host_impl.h
+++ b/content/browser/frame_host/render_frame_host_impl.h
@@ -245,9 +245,11 @@ class CONTENT_EXPORT RenderFrameHostImpl
   // active RenderFrames, but not until WasSwappedOut is called.
   void SwapOut(RenderFrameProxyHost* proxy, bool is_loading);
 
-  bool is_waiting_for_beforeunload_ack() const {
-    return is_waiting_for_beforeunload_ack_;
-  }
+  // Whether an ongoing navigation is waiting for a BeforeUnload ACK from the
+  // RenderFrame. Currently this only happens in cross-site navigations.
+  // PlzNavigate: this happens in every browser-initiated navigation that is not
+  // same-page.
+  bool IsWaitingForBeforeUnloadACK() const;
 
   // Whether the RFH is waiting for an unload ACK from the renderer.
   bool IsWaitingForUnloadACK() const;