Decouple X11WindowEventFilter into WindowEventFilter parent class.

ui/views/widget/desktop_aura/window_event_filter.h

Index: ui/views/widget/desktop_aura/window_event_filter.h
diff --git a/ui/views/widget/desktop_aura/window_event_filter.h b/ui/views/widget/desktop_aura/window_event_filter.h
new file mode 100644
index 0000000000000000000000000000000000000000..9d765cf73dd9b53e5cb37f04c66b4404cb262d8b
--- /dev/null
+++ b/ui/views/widget/desktop_aura/window_event_filter.h
@@ -0,0 +1,61 @@
+// 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 UI_VIEWS_WIDGET_DESKTOP_AURA_WINDOW_EVENT_FILTER_H_
+#define UI_VIEWS_WIDGET_DESKTOP_AURA_WINDOW_EVENT_FILTER_H_
+
+#include "base/compiler_specific.h"
+#include "base/macros.h"
+#include "base/message_loop/message_loop.h"
+#include "ui/events/event_handler.h"
+#include "ui/views/views_export.h"
+
+namespace views {
+class DesktopWindowTreeHost;
+
+// An EventFilter that sets properties on native windows.
+// The downstream effort to add wayland and x11 support with ozone
+// are using this class (to be upstreamed later).
+class VIEWS_EXPORT WindowEventFilter : public ui::EventHandler {
+ public:
+  explicit WindowEventFilter(DesktopWindowTreeHost* window_tree_host);
+  ~WindowEventFilter() override;
+
+  // Overridden from ui::EventHandler:
+  void OnMouseEvent(ui::MouseEvent* event) override;
+
+ private:
+  // Called when the user clicked the caption area.
+  void OnClickedCaption(ui::MouseEvent* event, int previous_click_component);
+
+  // Called when the user clicked the maximize button.
+  void OnClickedMaximizeButton(ui::MouseEvent* event);
+
+  void ToggleMaximizedState();
+
+  // Dispatches a message to the window manager to tell it to act as if a border
+  // or titlebar drag occurred with left mouse click. In case of X11, a
+  // _NET_WM_MOVERESIZE message is sent.
+  virtual void MaybeDispatchHostWindowDragMovement(int hittest,
+                                                   ui::MouseEvent* event);
+
+  // A signal to lower an attached to this filter window to the bottom of the
+  // stack.
+  virtual void LowerWindow();
+
+  DesktopWindowTreeHost* window_tree_host_;
+
+  // The non-client component for the target of a MouseEvent. Mouse events can
+  // be destructive to the window tree, which can cause the component of a
+  // ui::EF_IS_DOUBLE_CLICK event to no longer be the same as that of the
+  // initial click. Acting on a double click should only occur for matching
+  // components.
+  int click_component_;
+
+  DISALLOW_COPY_AND_ASSIGN(WindowEventFilter);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_WIDGET_DESKTOP_AURA_WINDOW_EVENT_FILTER_H_