Enhance RTCUIApplicationStatusObserver thread safety.

webrtc/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoEncoderH264.mm

Index: webrtc/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoEncoderH264.mm
diff --git a/webrtc/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoEncoderH264.mm b/webrtc/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoEncoderH264.mm
index 0fcefeef0271d543c3976aee0c1e9f9dcac5e6f1..3bf60fa551eb3770c4ac87d0e76a36adf84d1981 100644
--- a/webrtc/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoEncoderH264.mm
+++ b/webrtc/sdk/objc/Framework/Classes/VideoToolbox/RTCVideoEncoderH264.mm
@@ -301,6 +301,11 @@ CFStringRef ExtractProfile(const cricket::VideoCodec &codec) {
     _profile = ExtractProfile([codecInfo nativeVideoCodec]);
     LOG(LS_INFO) << "Using profile " << CFStringToString(_profile);
     RTC_CHECK([codecInfo.name isEqualToString:@"H264"]);
+
+#if defined(WEBRTC_IOS)
+    __unused RTCUIApplicationStatusObserver *observer =
+        [RTCUIApplicationStatusObserver sharedInstance];
+#endif

[kthelgason, 2017/09/13 08:20:09]

I think this needs a comment to explain to future generations what's going on.

We could also add a class method with a clearer name like `initialize`. Then it
may be obvious what's going on without a comment.

[andersc, 2017/09/13 08:46:21]

Good idea. I named the method `prepareForUse` since `initialize` clashes with
the method
https://developer.apple.com/documentation/objectivec/nsobject/1418639-initial...

   }
   return self;
 }