views: Add support for absolute positioned overlay views.

To test:
Run `cefclient.exe --use-views --hide-frame --hide-controls`
Add `--enable-chrome-runtime` for the same behavior using the Chrome location
bar instead of a text field.

tests/cefclient/browser/views_overlay_controls.h

@@ -0,0 +1,71 @@
+// Copyright (c) 2021 The Chromium Embedded Framework Authors. All rights
+// reserved. Use of this source code is governed by a BSD-style license that
+// can be found in the LICENSE file.
+
+#ifndef CEF_TESTS_CEFCLIENT_BROWSER_VIEWS_OVERLAY_CONTROLS_H_
+#define CEF_TESTS_CEFCLIENT_BROWSER_VIEWS_OVERLAY_CONTROLS_H_
+#pragma once
+
+#include "include/views/cef_button_delegate.h"
+#include "include/views/cef_label_button.h"
+#include "include/views/cef_menu_button.h"
+#include "include/views/cef_overlay_controller.h"
+#include "include/views/cef_panel.h"
+
+namespace client {
+
+// Implements window overlay controls that receive absolute positioning on top
+// of the browser view. All methods must be called on the browser process UI
+// thread.
+class ViewsOverlayControls : public CefButtonDelegate {
+ public:
+  enum class Command {
+    kMinimize = 1,
+    kMaximize,
+    kClose,
+  };
+
+  ViewsOverlayControls();
+
+  void Initialize(CefRefPtr<CefWindow> window,
+                  CefRefPtr<CefMenuButton> menu_button,
+                  CefRefPtr<CefView> location_bar,
+                  bool is_chrome_toolbar);
+  void Destroy();
+
+  // Update window control button state and location bar bounds.
+  void UpdateControls();
+
+  // Exclude all regions obscured by overlays.
+  void UpdateDraggableRegions(std::vector<CefDraggableRegion>& window_regions);
+
+ private:
+  // CefButtonDelegate methods:
+  void OnButtonPressed(CefRefPtr<CefButton> button) override;
+
+  CefRefPtr<CefLabelButton> CreateButton(Command command);
+
+  void MaybeUpdateMaximizeButton();
+
+  CefRefPtr<CefWindow> window_;
+  bool window_maximized_;
+
+  // Window control buttons.
+  CefRefPtr<CefPanel> panel_;
+  CefRefPtr<CefOverlayController> panel_controller_;
+
+  // Location bar.
+  CefRefPtr<CefView> location_bar_;
+  bool is_chrome_toolbar_;
+  CefRefPtr<CefOverlayController> location_controller_;
+
+  // Menu button.
+  CefRefPtr<CefOverlayController> menu_controller_;
+
+  IMPLEMENT_REFCOUNTING(ViewsOverlayControls);
+  DISALLOW_COPY_AND_ASSIGN(ViewsOverlayControls);
+};
+
+}  // namespace client
+
+#endif  // CEF_TESTS_CEFCLIENT_BROWSER_VIEWS_OVERLAY_CONTROLS_H_