Fix MediaDevices* tests dependency on BrowserThread globals after ~BrowserThreadImpl().

content/browser/renderer_host/media/media_devices_manager_unittest.cc

Index: content/browser/renderer_host/media/media_devices_manager_unittest.cc
diff --git a/content/browser/renderer_host/media/media_devices_manager_unittest.cc b/content/browser/renderer_host/media/media_devices_manager_unittest.cc
index cdbac6481a7c736508aef10fa09428902b7fd0a1..202b829b0a117e67f20782599ddb23191dc5966c 100644
--- a/content/browser/renderer_host/media/media_devices_manager_unittest.cc
+++ b/content/browser/renderer_host/media/media_devices_manager_unittest.cc
@@ -125,8 +125,8 @@ class MockMediaDeviceChangeSubscriber : public MediaDeviceChangeSubscriber {
 class MediaDevicesManagerTest : public ::testing::Test {
  public:
   MediaDevicesManagerTest()
-      : video_capture_device_factory_(nullptr),
-        thread_bundle_(content::TestBrowserThreadBundle::IO_MAINLOOP) {}
+      : thread_bundle_(content::TestBrowserThreadBundle::IO_MAINLOOP),
+        video_capture_device_factory_(nullptr) {}
   ~MediaDevicesManagerTest() override {}
 
   MOCK_METHOD1(MockCallback, void(const MediaDeviceEnumeration&));
@@ -156,10 +156,13 @@ class MediaDevicesManagerTest : public ::testing::Test {
         type, MediaDevicesManager::CachePolicy::SYSTEM_MONITOR);
   }
 
+  // Must outlive MediaDevicesManager as ~MediaDevicesManager() verifies it's
+  // running on the IO thread.
+  TestBrowserThreadBundle thread_bundle_;
+
   std::unique_ptr<MediaDevicesManager> media_devices_manager_;
   scoped_refptr<VideoCaptureManager> video_capture_manager_;
   MockVideoCaptureDeviceFactory* video_capture_device_factory_;
-  TestBrowserThreadBundle thread_bundle_;
   std::unique_ptr<MockAudioManager, media::AudioManagerDeleter> audio_manager_;
 
  private: