Fixes crash in RemoteWindowTreeHostWin::HandleActivateDesktop

chrome/browser/metro_viewer/chrome_metro_viewer_process_host_aurawin.cc

 // Copyright 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/metro_viewer/chrome_metro_viewer_process_host_aurawin.h"
 
 #include "ash/display/display_info.h"
 #include "ash/display/display_manager.h"
 #include "ash/host/ash_remote_window_tree_host_win.h"
 #include "ash/shell.h"
@@ skipping 16 matching lines @@
 #include "chrome/browser/ui/host_desktop.h"
 #include "chrome/browser/ui/tabs/tab_strip_model.h"
 #include "chrome/common/env_vars.h"
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/gpu_data_manager.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/browser/page_navigator.h"
 #include "content/public/browser/web_contents.h"
 #include "ui/aura/remote_window_tree_host_win.h"
 #include "ui/gfx/win/dpi.h"
+#include "ui/metro_viewer/metro_viewer_messages.h"
 #include "url/gurl.h"
 
 namespace {
 
 void CloseOpenAshBrowsers() {
   BrowserList* browser_list =
       BrowserList::GetInstance(chrome::HOST_DESKTOP_TYPE_ASH);
   if (browser_list) {
     for (BrowserList::const_iterator i = browser_list->begin();
          i != browser_list->end(); ++i) {
@@ skipping 12 matching lines @@
       ProfileManager::GetActiveUserProfile(),
       GURL(url),
       content::PAGE_TRANSITION_TYPED);
   params.disposition = NEW_FOREGROUND_TAB;
   params.host_desktop_type = chrome::HOST_DESKTOP_TYPE_ASH;
   chrome::Navigate(&params);
 }
 
 }  // namespace
 
+void HandleActivateDesktop(const base::FilePath& path, bool ash_exit) {
+  if (ChromeMetroViewerProcessHost::instance()) {
+    ChromeMetroViewerProcessHost::instance()->Send(
+        new MetroViewerHostMsg_ActivateDesktop(path, ash_exit));
+  }
+}
+
+// static
+ChromeMetroViewerProcessHost* ChromeMetroViewerProcessHost::instance_ = NULL;
+
 ChromeMetroViewerProcessHost::ChromeMetroViewerProcessHost()
     : MetroViewerProcessHost(
           content::BrowserThread::GetMessageLoopProxyForThread(
               content::BrowserThread::IO)) {
   chrome::IncrementKeepAliveCount();
+  DCHECK(instance_ == NULL);
+  instance_ = this;
+}
+
+ChromeMetroViewerProcessHost::~ChromeMetroViewerProcessHost() {
+  DCHECK(instance_ == this);
+  instance_ = NULL;
 }
 
 void ChromeMetroViewerProcessHost::OnChannelError() {
   // TODO(cpu): At some point we only close the browser. Right now this
   // is very convenient for developing.
   DVLOG(1) << "viewer channel error : Quitting browser";
 
   // Unset environment variable to let breakpad know that metro process wasn't
   // connected.
   ::SetEnvironmentVariableA(env_vars::kMetroConnected, NULL);
@@ skipping 71 matching lines @@
 void ChromeMetroViewerProcessHost::OnWindowSizeChanged(uint32 width,
                                                        uint32 height) {
   std::vector<ash::DisplayInfo> info_list;
   info_list.push_back(ash::DisplayInfo::CreateFromSpec(
       base::StringPrintf("%dx%d*%f", width, height, gfx::GetDPIScale())));
   ash::Shell::GetInstance()->display_manager()->OnNativeDisplaysChanged(
       info_list);
   aura::RemoteWindowTreeHostWin::Instance()->HandleWindowSizeChanged(width,
                                                                      height);
 }