fix: draggable regions exclusively on BrowserViews (#26145)

shell/browser/extended_web_contents_observer.h

@@ -0,0 +1,35 @@
+// Copyright (c) 2020 Microsoft, Inc.
+// Use of this source code is governed by the MIT license that can be
+// found in the LICENSE file.
+
+#ifndef SHELL_BROWSER_EXTENDED_WEB_CONTENTS_OBSERVER_H_
+#define SHELL_BROWSER_EXTENDED_WEB_CONTENTS_OBSERVER_H_
+
+#include <vector>
+
+#include "base/observer_list.h"
+#include "base/strings/string16.h"
+#include "electron/shell/common/api/api.mojom.h"
+#include "ui/gfx/geometry/rect.h"
+
+namespace electron {
+
+// Certain events are only in WebContentsDelegate, so we provide our own
+// Observer to dispatch those events.
+class ExtendedWebContentsObserver : public base::CheckedObserver {
+ public:
+  virtual void OnCloseContents() {}
+  virtual void OnDraggableRegionsUpdated(
+      const std::vector<mojom::DraggableRegionPtr>& regions) {}
+  virtual void OnSetContentBounds(const gfx::Rect& rect) {}
+  virtual void OnActivateContents() {}
+  virtual void OnPageTitleUpdated(const base::string16& title,
+                                  bool explicit_set) {}
+
+ protected:
+  ~ExtendedWebContentsObserver() override {}
+};
+
+}  // namespace electron
+
+#endif  // SHELL_BROWSER_EXTENDED_WEB_CONTENTS_OBSERVER_H_