Revert of Remove the is_loading_ field from WebContentsImpl

content/browser/frame_host/frame_tree_node.h

Index: content/browser/frame_host/frame_tree_node.h
diff --git a/content/browser/frame_host/frame_tree_node.h b/content/browser/frame_host/frame_tree_node.h
index 4ea612350f35ebecf80f0d3ec8736c5212fa620a..eac49777a663150917ab2289073e2dd3f8dc4d6b 100644
--- a/content/browser/frame_host/frame_tree_node.h
+++ b/content/browser/frame_host/frame_tree_node.h
@@ -235,11 +235,7 @@
   // A RenderFrameHost in this node started loading.
   // |to_different_document| will be true unless the load is a fragment
   // navigation, or triggered by history.pushState/replaceState.
-  // |was_previously_loading| is false if the FrameTree was not loading before.
-  // The caller is required to provide this boolean as the delegate should only
-  // be called if the FrameTree went from non-loading to loading state.
-  // However, when it is called, the FrameTree should be in a loading state.
-  void DidStartLoading(bool to_different_document, bool was_previously_loading);
+  void DidStartLoading(bool to_different_document);
 
   // A RenderFrameHost in this node stopped loading.
   void DidStopLoading();
@@ -260,10 +256,6 @@
   // Called when this node becomes focused.  Updates the node's last focused
   // time and notifies observers.
   void DidFocus();
-
-  // Called when the user closed the modal dialogue for BeforeUnload and
-  // cancelled the navigation. This should stop the loads.
-  void BeforeUnloadCanceled();
 
  private:
   class OpenerDestroyedObserver;