Makes ash/wm/common a library

ash/wm/common/wm_lookup.h

Index: ash/wm/common/wm_lookup.h
diff --git a/ash/wm/common/wm_lookup.h b/ash/wm/common/wm_lookup.h
new file mode 100644
index 0000000000000000000000000000000000000000..dfb953c6cf979715a9406c076acb91f69f2e30b2
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+++ b/ash/wm/common/wm_lookup.h
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+// 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 ASH_WM_COMMON_WM_LOOKUP_H_
+#define ASH_WM_COMMON_WM_LOOKUP_H_
+
+#include <stdint.h>
+
+#include "ash/wm/common/ash_wm_common_export.h"
+
+namespace views {
+class Widget;
+}
+
+namespace ash {
+namespace wm {
+
+class WmRootWindowController;
+class WmWindow;
+
+// WmLookup is used to lookup various wm types.
+class ASH_WM_COMMON_EXPORT WmLookup {
+ public:
+  static void Set(WmLookup* lookup);
+  static WmLookup* Get();
+
+  // Returns the WmRootWindowController with the specified display id, or null
+  // if there isn't one.
+  virtual WmRootWindowController* GetRootWindowControllerWithDisplayId(
+      int64_t id) = 0;
+
+  // Returns the WmWindow for the specified widget.
+  virtual WmWindow* GetWindowForWidget(views::Widget* widget) = 0;
+
+ protected:
+  virtual ~WmLookup() {}
+
+ private:
+  static WmLookup* instance_;
+};
+
+}  // namespace wm
+}  // namespace ash
+
+#endif  // ASH_WM_COMMON_WM_LOOKUP_H_