Added common layout framework for system menu rows.

ash/common/system/tray/size_range_layout.h

Index: ash/common/system/tray/size_range_layout.h
diff --git a/ash/common/system/tray/size_range_layout.h b/ash/common/system/tray/size_range_layout.h
new file mode 100644
index 0000000000000000000000000000000000000000..f59b25e25257b13cfad388e8ded62ba150dd1649
--- /dev/null
+++ b/ash/common/system/tray/size_range_layout.h
@@ -0,0 +1,112 @@
+// Copyright 2016 The Chromium Authors. All rights reserved.

[tdanderson, 2016/10/19 18:30:59]

Can you include a bug number in the CL description? Maybe file a new one to
track changes common to the layout of various rows.

[bruthig, 2016/10/20 04:40:12]

Done.

+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef ASH_COMMON_SYSTEM_TRAY_SIZE_RANGE_LAYOUT_H_
+#define ASH_COMMON_SYSTEM_TRAY_SIZE_RANGE_LAYOUT_H_
+
+#include <memory>
+
+#include "ash/ash_export.h"
+#include "base/macros.h"
+#include "ui/gfx/geometry/size.h"
+#include "ui/views/layout/layout_manager.h"
+
+namespace views {
+class View;
+}  // namespace views
+
+namespace ash {
+
+// A LayoutManager adapter that allows clients to specify a minimum and/or a
+// maximum preferred size. The actual layout will be delegated to the
+// LayoutManager owned by this. i.e. this can be used to override the preferred

[tdanderson, 2016/10/19 18:30:59]

nit: |this| instead of 'this'.

[bruthig, 2016/10/20 04:40:12]

Done.

+// size returned by a View.
+//
+// By default the SizeRangeLayout is configured to own a FillLayout but this can
+// be overridden with SetLayoutManager().
+//
+// Example use case :
+//
+//  Suppose you wanted a Label to take up a specific size of (50, 50) even
+//  though the label's preferred size was (25, 25).
+//
+// Example code:
+//
+//  Label* label = new Label(kSomeDummyText);
+//  View* container = new View();
+//  container->AddChildView(label);
+//  SizeRangeLayout* layout = new SizeRangeLayout();
+//  layout->SetSize(gfx::Size(50, 50));
+//  container->SetLayoutManager(layout);
+//
+class ASH_EXPORT SizeRangeLayout : public views::LayoutManager {
+ public:
+  // The absolute minimum width/height.
+  static const int kMinSize;

[tdanderson, 2016/10/19 18:30:59]

I don't think that |kMinSize| and |kMaxSize| need to be exposed in the header.
Perhaps they could just be defined locally in the MinSize() and MaxSize()
functions instead?

[bruthig, 2016/10/20 04:40:12]

Done.

+
+  // The absolute maximum width/height.
+  static const int kMaxSize;
+
+  // Returns the absolute minimum possible size. Use this with set_min_size() to
+  // effectively unset the minimum preferred size.
+  static gfx::Size MinSize();
+
+  // Returns the absolute maximum possible size. Use this with set_max_size() to
+  // effectively unset the maximum preferred size.
+  static gfx::Size MaxSize();

[tdanderson, 2016/10/19 18:30:59]

I'm also not sure whether MinSize() and MaxSize() really need to be exposed in
the header either. It seems the only place they're used is by
SizeRangeLayoutTest. Maybe move them private since SRLT is a friend? If you do
move them to private, consider adding public ResetMinSize() and ResetMaxSize()
functions (which would call out to set_min/max_size() as you describe in the
comments above).

If you are keeping MinSize() and MaxSize(), I suggest naming them something
different, since I think their current names make them too much like accessors.

nit: set_min_size() in the documentation should be SetMinSize() instead.

[bruthig, 2016/10/20 04:40:12]

I don't want to move them to private because I envision them being used by other
clients if they ever want to un-set a min/max OR more likely they want to only
set a min/max for one axis.  The following example would effectively only set an
x-axis max size.

gfx::Size max_size = SRL::MaxSize();
max_size.set_width(25);
layout.SetMaxSize(max_size);

I've renamed them, WDYT?

[tdanderson, 2016/10/20 18:16:48]

OK, sounds reasonable and the new names lg.

+
+  // Create a layout with no minimum or maximum preferred size.
+  SizeRangeLayout();
+
+  // Create a layout with the given minimum and maximum preferred sizes.
+  SizeRangeLayout(const gfx::Size& min_size, const gfx::Size& max_size);
+
+  ~SizeRangeLayout() override;
+
+  // Sets both the minimum and maximum preferred size.
+  void SetSize(const gfx::Size& size);
+
+  // Set the minimum preferred size that GetPreferredSize() will round up to.
+  void SetMinSize(const gfx::Size& size);
+
+  // Set the minimum preferred size that GetPreferredSize() will round down to.
+  void SetMaxSize(const gfx::Size& size);
+
+  // Sets the layout manager that actually performs the layout once the bounds
+  // have been defined.
+  void SetLayoutManager(std::unique_ptr<LayoutManager> layout_manager);
+
+  // LayoutManager:
+  void Installed(views::View* host) override;
+  void Layout(views::View* host) override;
+  gfx::Size GetPreferredSize(const views::View* host) const override;
+  int GetPreferredHeightForWidth(const views::View* host,
+                                 int width) const override;
+  void ViewAdded(views::View* host, views::View* view) override;
+  void ViewRemoved(views::View* host, views::View* view) override;
+
+ private:
+  friend class SizeRangeLayoutTest;
+
+  // Clamps |size| to be within the minimum and maximum preferred sizes.
+  void ClampSizeToRange(gfx::Size* size) const;
+
+  // The host View that this has been installed on.
+  views::View* host_ = nullptr;
+
+  // The layout manager that actually performs the layout.
+  std::unique_ptr<views::LayoutManager> layout_manager_;
+
+  // The minimum preferred size.
+  gfx::Size min_size_;
+
+  // The maximum preferred size.
+  gfx::Size max_size_;
+
+  DISALLOW_COPY_AND_ASSIGN(SizeRangeLayout);
+};
+
+}  // namespace ash
+
+#endif  // ASH_COMMON_SYSTEM_TRAY_SIZE_RANGE_LAYOUT_H_