Fix crash in AudioDeviceUtilityIOS::~AudioDeviceUtilityIOS.

BUG=3581
R=glaznev@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/16109004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@6732 4adac7df-926f-26a2-2b94-8c16560cd09d
diff --git a/modules/audio_device/ios/audio_device_utility_ios.cc b/modules/audio_device/ios/audio_device_utility_ios.cc
index 673246d..3362817 100644
--- a/modules/audio_device/ios/audio_device_utility_ios.cc
+++ b/modules/audio_device/ios/audio_device_utility_ios.cc
@@ -27,8 +27,9 @@
 AudioDeviceUtilityIOS::~AudioDeviceUtilityIOS() {
     WEBRTC_TRACE(kTraceMemory, kTraceAudioDevice, _id,
                  "%s destroyed", __FUNCTION__);
-    CriticalSectionScoped lock(&_critSect);
-
+    {
+        CriticalSectionScoped lock(&_critSect);
+    }
     delete &_critSect;
 }