Fixing some of the issues found by clang static analyzer.

Bug: webrtc:8737
Change-Id: Ib436449c493336e7c35a72a96dc88cccdbb5bbaf
Reviewed-on: https://webrtc-review.googlesource.com/39200
Commit-Queue: Peter Hanspers <peterhanspers@webrtc.org>
Reviewed-by: Henrik Andreassson <henrika@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#21607}
diff --git a/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodec.h b/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodec.h
index ab17ce4..470eb02 100644
--- a/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodec.h
+++ b/sdk/objc/Framework/Headers/WebRTC/RTCVideoCodec.h
@@ -148,7 +148,7 @@
                        numberOfCores:(int)numberOfCores;
 - (NSInteger)releaseEncoder;
 - (NSInteger)encode:(RTCVideoFrame *)frame
-    codecSpecificInfo:(id<RTCCodecSpecificInfo>)info
+    codecSpecificInfo:(nullable id<RTCCodecSpecificInfo>)info
            frameTypes:(NSArray<NSNumber *> *)frameTypes;
 - (int)setBitrate:(uint32_t)bitrateKbit framerate:(uint32_t)framerate;
 - (NSString *)implementationName;
@@ -171,7 +171,7 @@
 - (NSInteger)decode:(RTCEncodedImage *)encodedImage
           missingFrames:(BOOL)missingFrames
     fragmentationHeader:(RTCRtpFragmentationHeader *)fragmentationHeader
-      codecSpecificInfo:(__nullable id<RTCCodecSpecificInfo>)info
+      codecSpecificInfo:(nullable id<RTCCodecSpecificInfo>)info
            renderTimeMs:(int64_t)renderTimeMs;
 - (NSString *)implementationName;