Restore type attributes and remove extraneous nullability annotations for Objective-C Mac build

webrtc/api/objc/RTCPeerConnection+Stats.mm

 /*
  *  Copyright 2015 The WebRTC project authors. All Rights Reserved.
  *
  *  Use of this source code is governed by a BSD-style license
  *  that can be found in the LICENSE file in the root of the source
  *  tree. An additional intellectual property rights grant can be found
  *  in the file PATENTS.  All contributing project authors may
  *  be found in the AUTHORS file in the root of the source tree.
  */
 
 #import "webrtc/api/objc/RTCPeerConnection+Private.h"
 
 #include "webrtc/base/checks.h"
 
 #import "webrtc/api/objc/RTCMediaStreamTrack+Private.h"
 #import "webrtc/api/objc/RTCStatsReport+Private.h"
 #import "webrtc/base/objc/NSString+StdString.h"
 
-// TODO(hjon): Update nullability types. See http://crbug/webrtc/5592
-
 namespace webrtc {
 
 class StatsObserverAdapter : public StatsObserver {
  public:
   StatsObserverAdapter(void (^completionHandler)
-      (NSArray *stats)) {
-      // (NSArray<RTCStatsReport *> *stats)) {
+      (NSArray<RTCStatsReport *> *stats)) {
     completion_handler_ = completionHandler;
   }
 
   ~StatsObserverAdapter() {
     completion_handler_ = nil;
   }
 
   void OnComplete(const StatsReports& reports) override {
     RTC_DCHECK(completion_handler_);
     NSMutableArray *stats = [NSMutableArray arrayWithCapacity:reports.size()];
     for (const auto* report : reports) {
       RTCStatsReport *statsReport =
           [[RTCStatsReport alloc] initWithNativeReport:*report];
       [stats addObject:statsReport];
     }
     completion_handler_(stats);
     completion_handler_ = nil;
   }
 
  private:
-  void (^completion_handler_)(NSArray *stats);
-  // void (^completion_handler_)(NSArray<RTCStatsReport *> *stats);
+  void (^completion_handler_)(NSArray<RTCStatsReport *> *stats);
 };
 }  // namespace webrtc
 
 @implementation RTCPeerConnection (Stats)
 
 - (void)statsForTrack:(RTCMediaStreamTrack *)mediaStreamTrack
      statsOutputLevel:(RTCStatsOutputLevel)statsOutputLevel
     completionHandler:
-    (void (^)(NSArray *stats))completionHandler {
-    // (void (^)(NSArray<RTCStatsReport *> *stats))completionHandler {
+    (void (^)(NSArray<RTCStatsReport *> *stats))completionHandler {
   rtc::scoped_refptr<webrtc::StatsObserverAdapter> observer(
       new rtc::RefCountedObject<webrtc::StatsObserverAdapter>
           (completionHandler));
   webrtc::PeerConnectionInterface::StatsOutputLevel nativeOutputLevel =
       [[self class] nativeStatsOutputLevelForLevel:statsOutputLevel];
   self.nativePeerConnection->GetStats(
       observer, mediaStreamTrack.nativeTrack, nativeOutputLevel);
 }
 
 @end