mash: Fix a mash_browser_tests crash on x11.

chrome/browser/chrome_browser_main_extra_parts_x11.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/chrome_browser_main_extra_parts_x11.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/debugger.h"
 #include "base/location.h"
@@ skipping 81 matching lines @@
   ui::SetX11ErrorHandlers(NULL, NULL);
 }
 
 void ChromeBrowserMainExtraPartsX11::PostMainMessageLoopStart() {
   // Installs the X11 error handlers for the browser process after the
   // main message loop has started. This will allow us to exit cleanly
   // if X exits before us.
   ui::SetX11ErrorHandlers(BrowserX11ErrorHandler, BrowserX11IOErrorHandler);
 
 #if !defined(OS_CHROMEOS)
-  // Get a timestamp from the X server.  This makes our requests to the server
-  // less likely to be thrown away by the window manager.  Put the timestamp in
-  // a command line flag so we can forward it to an existing browser process if
-  // necessary.
-  base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
-      switches::kWmUserTimeMs,
-      base::Uint64ToString(
-          ui::X11EventSource::GetInstance()->UpdateLastSeenServerTime()));
+  // It is possible for X11EventSource to not have been created (e.g. when
+  // running as a mus client).
+  if (ui::X11EventSource::GetInstance()) {
+    // Get a timestamp from the X server.  This makes our requests to the server
+    // less likely to be thrown away by the window manager.  Put the timestamp
+    // in a command line flag so we can forward it to an existing browser
+    // process if necessary.
+    base::CommandLine::ForCurrentProcess()->AppendSwitchASCII(
+        switches::kWmUserTimeMs,
+        base::Uint64ToString(
+            ui::X11EventSource::GetInstance()->UpdateLastSeenServerTime()));
+  }
 #endif
 }
 
 void ChromeBrowserMainExtraPartsX11::PostMainMessageLoopRun() {
   // Unset the X11 error handlers. The X11 error handlers log the errors using a
   // |PostTask()| on the message-loop. But since the message-loop is in the
   // process of terminating, this can cause errors.
   ui::SetX11ErrorHandlers(X11EmptyErrorHandler, X11EmptyIOErrorHandler);
 }