Makes ash/wm/common a library

ash/wm/aura/wm_lookup_aura.cc

Index: ash/wm/aura/wm_lookup_aura.cc
diff --git a/ash/wm/aura/wm_lookup_aura.cc b/ash/wm/aura/wm_lookup_aura.cc
new file mode 100644
index 0000000000000000000000000000000000000000..1ddaa78fa2626bc0cc8153a8a62b534a9ff09b22
--- /dev/null
+++ b/ash/wm/aura/wm_lookup_aura.cc
@@ -0,0 +1,36 @@
+// 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 "ash/wm/aura/wm_lookup_aura.h"
+
+#include "ash/display/window_tree_host_manager.h"
+#include "ash/shell.h"
+#include "ash/wm/aura/wm_root_window_controller_aura.h"
+#include "ash/wm/aura/wm_window_aura.h"
+#include "ash/wm/common/wm_layout_manager.h"
+
+namespace ash {
+namespace wm {
+
+WmLookupAura::WmLookupAura() {
+  WmLookup::Set(this);
+}
+
+WmLookupAura::~WmLookupAura() {
+  WmLookup::Set(nullptr);
+}
+
+WmRootWindowController* WmLookupAura::GetRootWindowControllerWithDisplayId(
+    int64_t id) {
+  return WmRootWindowControllerAura::Get(Shell::GetInstance()
+                                             ->window_tree_host_manager()
+                                             ->GetRootWindowForDisplayId(id));
+}
+
+WmWindow* WmLookupAura::GetWindowForWidget(views::Widget* widget) {
+  return WmWindowAura::Get(widget->GetNativeWindow());
+}
+
+}  // namespace wm
+}  // namespace ash