Remove balloon notification code. The last user was the Linux GTK port but that's deleted now.

chrome/browser/ui/gtk/notifications/balloon_view_host_gtk.h

Index: chrome/browser/ui/gtk/notifications/balloon_view_host_gtk.h
===================================================================
--- chrome/browser/ui/gtk/notifications/balloon_view_host_gtk.h	(revision 263011)
+++ chrome/browser/ui/gtk/notifications/balloon_view_host_gtk.h	(working copy)
@@ -1,31 +0,0 @@
-// 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 CHROME_BROWSER_UI_GTK_NOTIFICATIONS_BALLOON_VIEW_HOST_GTK_H_
-#define CHROME_BROWSER_UI_GTK_NOTIFICATIONS_BALLOON_VIEW_HOST_GTK_H_
-
-#include "chrome/browser/notifications/balloon_host.h"
-#include "ui/gfx/native_widget_types.h"
-
-// BalloonViewHost class is a delegate to the renderer host for the HTML
-// notification.  When initialized it creates a new RenderViewHost and loads
-// the contents of the toast into it.  It also handles links within the toast,
-// loading them into a new tab.
-class BalloonViewHost : public BalloonHost {
- public:
-  explicit BalloonViewHost(Balloon* balloon);
-
-  virtual ~BalloonViewHost();
-
-  // Changes the size of the balloon.
-  void UpdateActualSize(const gfx::Size& new_size);
-
-  // Accessors.
-  gfx::NativeView native_view() const;
-
- private:
-  DISALLOW_COPY_AND_ASSIGN(BalloonViewHost);
-};
-
-#endif  // CHROME_BROWSER_UI_GTK_NOTIFICATIONS_BALLOON_VIEW_HOST_GTK_H_