Reland change for aura tooltips that was revert due to build break:

ui/aura/client/tooltip_client.h

Index: ui/aura/client/tooltip_client.h
diff --git a/ui/aura/client/tooltip_client.h b/ui/aura/client/tooltip_client.h
new file mode 100644
index 0000000000000000000000000000000000000000..eb6db2cb86093516758b73f95f485a3c7c2c3fb3
--- /dev/null
+++ b/ui/aura/client/tooltip_client.h
@@ -0,0 +1,32 @@
+// 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.
+
+#ifndef UI_AURA_CLIENT_TOOLTIP_CLIENT_H_
+#define UI_AURA_CLIENT_TOOLTIP_CLIENT_H_
+#pragma once
+
+#include "ui/aura/aura_export.h"
+#include "ui/aura/event.h"
+#include "ui/gfx/font.h"
+
+namespace aura {
+
+class Window;
+
+class AURA_EXPORT TooltipClient {
+ public:
+  // Returns the default font used by tooltips.
+  static gfx::Font GetDefaultFont();
+
+  // Returns the maximum width of the tooltip. |x| and |y| give the location
+  // the tooltip is to be displayed on in screen coordinates.
+  static int GetMaxWidth(int x, int y);
+
+  // Informs the shell tooltip manager of change in tooltip for window |target|.
+  virtual void UpdateTooltip(Window* target) = 0;
+};
+
+}  // namespace aura
+
+#endif  // UI_AURA_CLIENT_TOOLTIP_CLIENT_H_