[OverlayWindow] Add platform-independent window and views implementation.

chrome/browser/ui/overlay/overlay_window.h

+// Copyright 2017 The Chromium 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 CHROME_BROWSER_UI_OVERLAY_OVERLAY_WINDOW_H_
+#define CHROME_BROWSER_UI_OVERLAY_OVERLAY_WINDOW_H_
+
+#include "ui/compositor/layer.h"

[sky, 2017/07/11 18:02:25]

forward declare this (assuming you need Layer, which I'm not sure you do).

[apacible, 2017/07/18 01:08:27]

Done. Included ui/gfx/native_widget_types.h because NativeWindow gets redefined.

+
+// This window will always float above other windows. The intention is to show
+// content perpetually while the user is still interacting with the other
+// browser windows.
+class OverlayWindow {
+ public:
+  OverlayWindow() {}
+  virtual ~OverlayWindow() {}

[mlamouri (slow - plz ping), 2017/07/07 10:34:38]

= default for both

[apacible, 2017/07/18 01:08:28]

Done.

+
+  // Returns a created OverlayWindow. This is defined in the platform-specific
+  // implementation for the class.
+  static std::unique_ptr<OverlayWindow> Create();
+
+  virtual void Init() = 0;
+  virtual bool IsActive() const = 0;
+  virtual void Show() = 0;
+  virtual void Hide() = 0;
+  virtual void Close() = 0;
+  virtual void Activate() = 0;
+  virtual bool IsAlwaysOnTop() const = 0;

[sky, 2017/07/11 18:02:25]

Is this really needed? Same question for GetLayer.

[apacible, 2017/07/18 01:08:28]

Yes, we want these both to be exposed.

+  virtual ui::Layer* GetLayer() = 0;
+  virtual gfx::NativeWindow GetNativeWindow() const = 0;
+  virtual gfx::Rect GetBounds() const = 0;
+
+ private:
+  DISALLOW_COPY_AND_ASSIGN(OverlayWindow);
+};
+
+#endif  // CHROME_BROWSER_UI_OVERLAY_OVERLAY_WINDOW_H_