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.cc

Index: chrome/browser/ui/gtk/notifications/balloon_view_host_gtk.cc
===================================================================
--- chrome/browser/ui/gtk/notifications/balloon_view_host_gtk.cc	(revision 263011)
+++ chrome/browser/ui/gtk/notifications/balloon_view_host_gtk.cc	(working copy)
@@ -1,37 +0,0 @@
-// Copyright (c) 2012 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 "chrome/browser/ui/gtk/notifications/balloon_view_host_gtk.h"
-
-#include <gtk/gtk.h>
-
-#include "chrome/browser/notifications/balloon.h"
-#include "content/public/browser/render_view_host.h"
-#include "content/public/browser/render_widget_host_view.h"
-#include "content/public/browser/web_contents.h"
-#include "content/public/browser/web_contents_view.h"
-
-BalloonViewHost::BalloonViewHost(Balloon* balloon)
-    : BalloonHost(balloon) {
-}
-
-BalloonViewHost::~BalloonViewHost() {
-  Shutdown();
-}
-
-void BalloonViewHost::UpdateActualSize(const gfx::Size& new_size) {
-  content::RenderViewHost* host = web_contents_->GetRenderViewHost();
-  if (host) {
-    content::RenderWidgetHostView* view = host->GetView();
-    if (view)
-      view->SetSize(new_size);
-  }
-
-  gtk_widget_set_size_request(
-      native_view(), new_size.width(), new_size.height());
-}
-
-gfx::NativeView BalloonViewHost::native_view() const {
-  return web_contents_->GetView()->GetNativeView();
-}