Fix crash when deleting workspaces

ui/aura_shell/workspace/workspace_manager.cc

 // 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.
 #include "ui/aura_shell/workspace/workspace_manager.h"
 
 #include <algorithm>
 
 #include "base/logging.h"
 #include "base/stl_util.h"
 #include "ui/aura_shell/workspace/workspace.h"
 
 namespace {
 
 // The horizontal margein between workspaces in pixels.
 const int kWorkspaceHorizontalMargin = 50;
 }
 
 namespace aura_shell {
 
 ////////////////////////////////////////////////////////////////////////////////
 // WindowManager, public:
 
 WorkspaceManager::WorkspaceManager()
     : active_workspace_(NULL) {
 }
 
 WorkspaceManager::~WorkspaceManager() {
-  STLDeleteElements(&workspaces_);
+  std::vector<Workspace*> copy_to_delete(workspaces_);
+  STLDeleteElements(&copy_to_delete);
 }
 
 Workspace* WorkspaceManager::CreateWorkspace() {
   return new Workspace(this);
 }
 
 Workspace* WorkspaceManager::GetActiveWorkspace() const {
   return active_workspace_;
 }
 
@@ skipping 49 matching lines @@
 
 void WorkspaceManager::SetActiveWorkspace(Workspace* workspace) {
   DCHECK(std::find(workspaces_.begin(),
                    workspaces_.end(),
                    workspace)
          != workspaces_.end());
   active_workspace_ = workspace;
 }
 
 }  // namespace aura_shell