Refactors std::vector<Display> out of ScreenMus

ui/views/mus/display_list.h

Index: ui/views/mus/display_list.h
diff --git a/ui/views/mus/display_list.h b/ui/views/mus/display_list.h
new file mode 100644
index 0000000000000000000000000000000000000000..19b0ac97f11bde342082075527285a71d31830d6
--- /dev/null
+++ b/ui/views/mus/display_list.h
@@ -0,0 +1,69 @@
+// 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_VIEWS_MUS_DISPLAY_LIST_H_
+#define UI_VIEWS_MUS_DISPLAY_LIST_H_
+
+#include <stdint.h>
+
+#include <vector>
+
+#include "base/observer_list.h"
+#include "mojo/public/cpp/bindings/binding.h"
+#include "ui/display/display.h"
+#include "ui/views/mus/mus_export.h"
+
+namespace display {
+class Display;
+class DisplayObserver;
+}
+
+namespace views {
+
+// Maintains an ordered list of display::Displays as well as operations to add,
+// remove and update said list. Additionally maintains display::DisplayObservers
+// and updates them as appropriate.
+class VIEWS_MUS_EXPORT DisplayList {
+ public:
+  using Displays = std::vector<display::Display>;
+
+  enum class Type {
+    PRIMARY,
+    NOT_PRIMARY,
+  };
+
+  DisplayList();
+  ~DisplayList();
+
+  void AddObserver(display::DisplayObserver* observer);
+  void RemoveObserver(display::DisplayObserver* observer);
+
+  const Displays& displays() const { return displays_; }
+
+  Displays::const_iterator FindDisplayById(int64_t id) const;
+  Displays::iterator FindDisplayById(int64_t id);
+
+  Displays::const_iterator GetPrimaryDisplayIterator() const;
+
+  // Updates the cached id based on display.id() as well as whether the Display
+  // is the primary display.
+  void UpdateDisplay(const display::Display& display, Type type);
+
+  // Adds a new Display.
+  void AddDisplay(const display::Display& display, Type type);
+
+  // Removes the Display with the specified id.
+  void RemoveDisplay(int64_t id);
+
+ private:
+  std::vector<display::Display> displays_;
+  int primary_display_index_ = -1;
+  base::ObserverList<display::DisplayObserver> observers_;
+
+  DISALLOW_COPY_AND_ASSIGN(DisplayList);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_MUS_DISPLAY_LIST_H_