aura: Make aura::TooltipClient completely static?

ui/aura/test/test_tooltip_client.cc

Index: ui/aura/test/test_tooltip_client.cc
diff --git a/ui/aura/test/test_tooltip_client.cc b/ui/aura/test/test_tooltip_client.cc
new file mode 100644
index 0000000000000000000000000000000000000000..b28aaa8014ee5a7766d26f9968080f8cbc7ba1bc
--- /dev/null
+++ b/ui/aura/test/test_tooltip_client.cc
@@ -0,0 +1,24 @@
+// Copyright (c) 2011 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 "ui/aura/client/tooltip_client.h"
+#include "ui/gfx/font.h"
+
+namespace aura {
+
+// static
+gfx::Font TooltipClient::GetDefaultFont() {
+  return gfx::Font();
+}
+
+// static
+int TooltipClient::GetMaxWidth(int x, int y) {
+  return 0;
+}
+
+// static
+void TooltipClient::UpdateTooltip(Window* target) {
+}
+
+}  // namespace aura