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

chrome/browser/notifications/fake_balloon_view.cc

-// 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/notifications/fake_balloon_view.h"
-
-FakeBalloonView::FakeBalloonView(Balloon* balloon)
-    : balloon_(balloon) {
-}
-
-FakeBalloonView::~FakeBalloonView() {
-}
-
-void FakeBalloonView::Show(Balloon* balloon) {
-}
-
-void FakeBalloonView::Update() {
-}
-
-void FakeBalloonView::RepositionToBalloon() {
-}
-
-void FakeBalloonView::Close(bool by_user) {
-  balloon_->OnClose(by_user);
-}
-
-gfx::Size FakeBalloonView::GetSize() const {
-  return balloon_->content_size();
-}
-
-BalloonHost* FakeBalloonView::GetHost() const {
-  return NULL;
-}