Adds WmLayoutManager and the aura wrapper AuraLayoutManagerAdapter

ash/wm/common/wm_layout_manager.h

+// Copyright 2016 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 ASH_WM_COMMON_WM_LAYOUT_MANAGER_H_
+#define ASH_WM_COMMON_WM_LAYOUT_MANAGER_H_
+
+#include "ash/ash_export.h"
+
+namespace gfx {
+class Rect;
+}
+
+namespace ash {
+namespace wm {
+
+class WmWindow;
+
+class ASH_EXPORT WmLayoutManager {

[James Cook, 2016/04/15 17:44:35]

nit: Class comment. What does this do and why must it exist?

[sky, 2016/04/15 19:26:36]

Ya, sorry. This is mostly transitional and I figured it was obvious. But you're
right. Added some comments.

+ public:
+  virtual ~WmLayoutManager() {}
+
+  // Invoked when the window is resized.
+  virtual void OnWindowResized() = 0;
+
+  // Invoked when the window |child| has been added.
+  virtual void OnWindowAddedToLayout(WmWindow* child) = 0;
+
+  // Invoked prior to removing |window|.
+  virtual void OnWillRemoveWindowFromLayout(WmWindow* child) = 0;
+
+  // Invoked after removing |window|.
+  virtual void OnWindowRemovedFromLayout(WmWindow* child) = 0;
+
+  // Invoked when the |SetVisible()| is invoked on the window |child|.

[James Cook, 2016/04/15 17:44:35]

nit: "when the |SetVisible()|" -> "when |SetVisible()|" or similar.

[sky, 2016/04/15 19:26:36]

Sorry, I copied this from aura. I've cleaned it all up.

+  // |visible| is the value supplied to |SetVisible()|. If |visible| is true,
+  // window->IsVisible() may still return false. See description in

[James Cook, 2016/04/15 17:44:35]

nit: Did you mean child->IsVisible()?

+  // Window::IsVisible() for details.

[James Cook, 2016/04/15 17:44:35]

nit: Which "Window" do you mean here? aura::Window? WmWindow? If the latter, the
comment is on WmWindow::GetTargetVisibility().

+  virtual void OnChildWindowVisibilityChanged(WmWindow* child,
+                                              bool visibile) = 0;
+
+  // Invoked when |WmWindow::SetBounds| is called on |child|.
+  // Implementation must call |SetChildBoundsDirect| to change the
+  // |child|'s bounds. LayoutManager may modify |requested_bounds|
+  // before applying, or ignore the request.
+  virtual void SetChildBounds(WmWindow* child,
+                              const gfx::Rect& requested_bounds) = 0;
+};
+
+}  // namespace wm
+}  // namespace ash
+
+#endif  // ASH_WM_COMMON_WM_LAYOUT_MANAGER_H_