Added common layout framework for system menu rows.

ash/common/system/tray/size_range_layout.cc

Index: ash/common/system/tray/size_range_layout.cc
diff --git a/ash/common/system/tray/size_range_layout.cc b/ash/common/system/tray/size_range_layout.cc
new file mode 100644
index 0000000000000000000000000000000000000000..ddb5b5bedda2401fbb5380315e8543a36e74d683
--- /dev/null
+++ b/ash/common/system/tray/size_range_layout.cc
@@ -0,0 +1,109 @@
+// 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.
+
+#include <limits>
+
+#include "ash/common/system/tray/size_range_layout.h"
+
+#include "base/logging.h"
+#include "ui/views/layout/fill_layout.h"
+
+namespace ash {
+
+// static
+
+const int SizeRangeLayout::kMinSize = 0;
+
+const int SizeRangeLayout::kMaxSize = std::numeric_limits<int>::max();
+
+gfx::Size SizeRangeLayout::MinSize() {
+  return gfx::Size(kMinSize, kMinSize);
+}
+
+gfx::Size SizeRangeLayout::MaxSize() {
+  return gfx::Size(kMaxSize, kMaxSize);
+}
+
+// Non static
+
+SizeRangeLayout::SizeRangeLayout() : SizeRangeLayout(MinSize(), MaxSize()) {}
+
+SizeRangeLayout::SizeRangeLayout(const gfx::Size& min_size,
+                                 const gfx::Size& max_size)
+    : layout_manager_(new views::FillLayout()) {
+  SetMinSize(min_size);
+  SetMaxSize(max_size);
+}
+
+SizeRangeLayout::~SizeRangeLayout() {}
+
+void SizeRangeLayout::SetSize(const gfx::Size& size) {
+  SetMinSize(size);
+  SetMaxSize(size);
+}
+
+void SizeRangeLayout::SetMinSize(const gfx::Size& size) {
+  min_size_ = size;
+  min_size_.SetToMax(gfx::Size());
+}
+
+void SizeRangeLayout::SetMaxSize(const gfx::Size& size) {
+  max_size_ = size;
+  min_size_.SetToMax(gfx::Size());

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

You probably wanted this to be |max_size_|

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

D'oh, done!

+}
+
+void SizeRangeLayout::SetLayoutManager(
+    std::unique_ptr<LayoutManager> layout_manager) {
+  layout_manager_ = std::move(layout_manager);
+  if (layout_manager_)
+    layout_manager_->Installed(host_);
+}
+
+void SizeRangeLayout::Installed(views::View* host) {
+  DCHECK(!host_);
+  host_ = host;
+  if (layout_manager_)
+    layout_manager_->Installed(host);
+}
+
+void SizeRangeLayout::Layout(views::View* host) {
+  if (layout_manager_)
+    layout_manager_->Layout(host);
+}
+
+gfx::Size SizeRangeLayout::GetPreferredSize(const views::View* host) const {
+  // TODO(bruthig): Handle Views that override GetPreferredSize().

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

As discussed in person, can you append something like "... to make
SizeRangeLayout suitable for general use in views"

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

Removed.

+  gfx::Size preferred_size =
+      layout_manager_ ? layout_manager_->GetPreferredSize(host) : gfx::Size();
+  ClampSizeToRange(&preferred_size);
+  return preferred_size;
+}
+
+int SizeRangeLayout::GetPreferredHeightForWidth(const views::View* host,
+                                                int width) const {
+  // TODO(bruthig): Handle Views that override GetPreferredSize().
+  const int height =
+      layout_manager_ ? layout_manager_->GetPreferredHeightForWidth(host, width)
+                      : 0;
+  gfx::Size size(0, height);
+  ClampSizeToRange(&size);
+  return size.height();
+}
+
+void SizeRangeLayout::ViewAdded(views::View* host, views::View* view) {
+  if (layout_manager_)

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

Regarding your 'if (layout_manager_)' checks in this file: if I understand
correctly, the only way |layout_manager_| can be null is if someone called
SetLayoutManager() with a null layout manager. Is that right? If so, how would
you feel about enforcing a non-null parameter in SetLayoutManager() with a
CHECK?

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

I've changed it to a DCHECK().  Do you think it's worth of a CHECK()?

With this change I am able to remove those two TODO's regarding Views preferred
size/height. :D

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

A DCHECK should be fine.

+    layout_manager_->ViewAdded(host, view);
+}
+
+void SizeRangeLayout::ViewRemoved(views::View* host, views::View* view) {
+  if (layout_manager_)
+    layout_manager_->ViewRemoved(host, view);
+}
+
+void SizeRangeLayout::ClampSizeToRange(gfx::Size* size) const {
+  size->SetToMax(min_size_);
+  size->SetToMin(max_size_);
+}
+
+}  // namespace ash