fix: make draggable regions work when devtools is opened on macOS (#26361)

* fix: make draggable region work when devtools is open

* fix: update draggable regions when resizing

shell/browser/extended_web_contents_observer.h

@@ -25,6 +25,7 @@ class ExtendedWebContentsObserver : public base::CheckedObserver {
   virtual void OnActivateContents() {}
   virtual void OnPageTitleUpdated(const base::string16& title,
                                   bool explicit_set) {}
+  virtual void OnDevToolsResized() {}
 
  protected:
   ~ExtendedWebContentsObserver() override {}