Remove implementation of Panels on OSes other than ChromeOS.

chrome/browser/ui/panels/panel_collection.cc

Index: chrome/browser/ui/panels/panel_collection.cc
diff --git a/chrome/browser/ui/panels/panel_collection.cc b/chrome/browser/ui/panels/panel_collection.cc
deleted file mode 100644
index 5c6e1245ec2b142d0cb14c666eceac31b82229a1..0000000000000000000000000000000000000000
--- a/chrome/browser/ui/panels/panel_collection.cc
+++ /dev/null
@@ -1,12 +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/panels/panel_collection.h"
-
-PanelCollection::PanelCollection(Type type)
-    : type_(type) {
-}
-
-PanelCollection::~PanelCollection() {
-}