Implements a display scale tray setting behind a chrome switch

ash/system/display_scale/scale_detailed_view.cc

Index: ash/system/display_scale/scale_detailed_view.cc
diff --git a/ash/system/display_scale/scale_detailed_view.cc b/ash/system/display_scale/scale_detailed_view.cc
new file mode 100644
index 0000000000000000000000000000000000000000..d16af621a16c8bdbcb3503ab7d434339b38cb938
--- /dev/null
+++ b/ash/system/display_scale/scale_detailed_view.cc
@@ -0,0 +1,81 @@
+// 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.
+
+#include "ash/system/display_scale/scale_detailed_view.h"
+
+#include "ash/shell.h"
+#include "ash/strings/grit/ash_strings.h"
+#include "ash/system/tray/hover_highlight_view.h"
+#include "ash/system/tray/tray_popup_utils.h"
+#include "base/command_line.h"
+#include "base/strings/stringprintf.h"
+#include "base/strings/utf_string_conversions.h"
+#include "ui/display/display.h"
+#include "ui/display/display_switches.h"
+#include "ui/display/manager/display_manager.h"
+#include "ui/views/controls/scroll_view.h"
+
+namespace ash {
+namespace tray {
+namespace {
+
+const double scales[] = {1.0f,  1.25f, 1.33f, 1.5f,  1.66f,
+                         1.75f, 1.9f,  2.0f,  2.25f, 2.5f};
+constexpr double kEpsilon = 0.01;
+
+bool IsSameScaleFactor(double new_value) {
+  return (std::abs(display::Display::GetForcedDeviceScaleFactor() - new_value) <
+          kEpsilon);
+}
+
+}  // namespace
+
+ScaleDetailedView::ScaleDetailedView(SystemTrayItem* owner)
+    : TrayDetailsView(owner) {
+  CreateScrollableList();
+  CreateTitleRow(IDS_ASH_STATUS_TRAY_SCALE);
+  UpdateScrollableList();
+  Layout();
+}
+
+ScaleDetailedView::~ScaleDetailedView() {}
+
+HoverHighlightView* ScaleDetailedView::AddScrollListItem(
+    const base::string16& text,
+    bool highlight,
+    bool checked) {
+  HoverHighlightView* container = new HoverHighlightView(this);
+
+  container->AddLabelRow(text);
+  TrayPopupUtils::InitializeAsCheckableRow(container, checked);
+
+  scroll_content()->AddChildView(container);
+  return container;
+}
+
+void ScaleDetailedView::UpdateScrollableList() {
+  scroll_content()->RemoveAllChildViews(true);
+  view_to_scale_.clear();
+
+  for (double scale : scales) {
+    HoverHighlightView* container = AddScrollListItem(
+        base::UTF8ToUTF16(base::StringPrintf("%.2f", scale)),
+        false /* highlight */, IsSameScaleFactor(scale) /* checkmark icon */);
+    view_to_scale_[container] = scale;
+  }
+}
+
+void ScaleDetailedView::HandleViewClicked(views::View* view) {
+  // The selected dsf is already active.
+  double new_scale = view_to_scale_[view];
+  if (IsSameScaleFactor(new_scale))
+    return;
+  display::Display::SetForceDeviceScaleFactor(new_scale);
+  ash::Shell::Get()->display_manager()->UpdateDisplays();
+  UpdateScrollableList();
+  Layout();
+}
+
+}  // namespace tray
+}  // namespace ash