Do DXVA pre-sandbox initialization off the main thread.

content/common/gpu/media/video_decode_accelerator_unittest.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.
 //
 // The bulk of this file is support code; sorry about that.  Here's an overview
 // to hopefully help readers of this code:
 // - RenderingHelper is charged with interacting with X11/{EGL/GLES2,GLX/GL} or
 //   Win/EGL.
 // - ClientState is an enum for the state of the decode client used by the test.
 // - ClientStateNotification is a barrier abstraction that allows the test code
@@ skipping 872 matching lines @@
     }
     if (it->first == "v" || it->first == "vmodule")
       continue;
     LOG(FATAL) << "Unexpected switch: " << it->first << ":" << it->second;
   }
 
   base::ShadowingAtExitManager at_exit_manager;
   content::RenderingHelper::InitializePlatform();
 
 #if defined(OS_WIN)
-  content::DXVAVideoDecodeAccelerator::PreSandboxInitialization();
+  base::WaitableEvent event(true, false);
+  content::DXVAVideoDecodeAccelerator::PreSandboxInitialization(
+      base::Bind(&base::WaitableEvent::Signal,
+                 base::Unretained(&event)));
+  event.Wait();
 #elif defined(OS_CHROMEOS) && defined(ARCH_CPU_ARMEL)
   content::OmxVideoDecodeAccelerator::PreSandboxInitialization();
 #elif defined(OS_CHROMEOS) && defined(ARCH_CPU_X86_FAMILY)
   content::VaapiVideoDecodeAccelerator::PreSandboxInitialization();
 #endif
 
   return RUN_ALL_TESTS();
 }