views: add layout delegates

ui/harmony/harmony_layout_delegate.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 UI_HARMONY_HARMONY_LAYOUT_DELEGATE_H_
+#define UI_HARMONY_HARMONY_LAYOUT_DELEGATE_H_
+
+#include "ui/harmony/harmony_export.h"
+#include "ui/views/layout/layout_delegate.h"
+
+namespace views {
+class View;
+}  // namespace views
+
+namespace ui {
+
+class HARMONY_EXPORT HarmonyLayoutDelegate : public views::LayoutDelegate {

[sky, 2016/11/08 23:34:00]

We are in the process of trying to cleanup the ui directory. The ui directory
should only contain the fundamental building blocks of UI components.  It should
not contain the UI features that are composed of those building blocks. I'm
inclined to think of harmony as not a fundamental building block, but something
that builds on views. As such I think this should be in components/harmony. If
only needed in chrome, then move there (but I suspect you'll want to use this in
ash code too, which means components/harmony).

+ public:
+  // Returns the singleton HarmonyLayoutDelegate instance.
+  static HarmonyLayoutDelegate* Get();
+
+  // Convenience function: if Harmony mode is enabled, sets the
+  // HarmonyLayoutDelegate singleton instance to be |view|'s LayoutDelegate.
+  static void ApplyToViewIfNeeded(views::View* view);
+
+  // views::LayoutDelegate:
+  int GetLayoutDistance(LayoutDistanceType type) const override;
+  bool UseExtraDialogPadding() const override;
+};
+
+}  // namespace ui
+
+#endif  // UI_HARMONY_HARMONY_LAYOUT_DELEGATE_H_