Re-fix http://crbug.com/87176, and add a test.

content/browser/browser_main_loop.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 "content/browser/browser_main_loop.h"
 
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/hi_res_timer_manager.h"
@@ skipping 247 matching lines @@
     HISTOGRAM_MEMORY_KB("Memory.BrowserUsed", private_bytes >> 10);
 #endif
   }
  private:
   DISALLOW_COPY_AND_ASSIGN(MemoryObserver);
 };
 
 
 // static
 media::AudioManager* BrowserMainLoop::GetAudioManager() {
-  return g_current_browser_main_loop->audio_manager_.get();
+  if (g_current_browser_main_loop)
+    return g_current_browser_main_loop->audio_manager_.get();
+  return NULL;
 }
 
 // static
 AudioMirroringManager* BrowserMainLoop::GetAudioMirroringManager() {
   return g_current_browser_main_loop->audio_mirroring_manager_.get();
 }
 
 // static
 MediaStreamManager* BrowserMainLoop::GetMediaStreamManager() {
-  return g_current_browser_main_loop->media_stream_manager_.get();
+  if (g_current_browser_main_loop)
+    return g_current_browser_main_loop->media_stream_manager_.get();
+  return NULL;
 }
 // BrowserMainLoop construction / destruction =============================
 
 BrowserMainLoop::BrowserMainLoop(const MainFunctionParams& parameters)
     : parameters_(parameters),
       parsed_command_line_(parameters.command_line),
       result_code_(RESULT_CODE_NORMAL_EXIT) {
   DCHECK(!g_current_browser_main_loop);
   g_current_browser_main_loop = this;
 }
@@ skipping 617 matching lines @@
   if (parameters_.ui_task)
     base::MessageLoopForUI::current()->PostTask(FROM_HERE,
                                                 *parameters_.ui_task);
 
   base::RunLoop run_loop;
   run_loop.Run();
 #endif
 }
 
 }  // namespace content