Replace scoped_ptr with unique_ptr everywhere

But keep #including scoped_ptr.h in .h files, so as not to break
WebRTC users who expect those .h files to give them rtc::scoped_ptr.

BUG=webrtc:5520

Review-Url: https://codereview.webrtc.org/1937693002
Cr-Commit-Position: refs/heads/master@{#12581}
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCDataChannel.mm b/webrtc/sdk/objc/Framework/Classes/RTCDataChannel.mm
index cdc7e98..9948615 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCDataChannel.mm
+++ b/webrtc/sdk/objc/Framework/Classes/RTCDataChannel.mm
@@ -12,7 +12,7 @@
 
 #import "NSString+StdString.h"
 
-#include "webrtc/base/scoped_ptr.h"
+#include <memory>
 
 namespace webrtc {
 
@@ -46,7 +46,7 @@
 
 
 @implementation RTCDataBuffer {
-  rtc::scoped_ptr<webrtc::DataBuffer> _dataBuffer;
+  std::unique_ptr<webrtc::DataBuffer> _dataBuffer;
 }
 
 - (instancetype)initWithData:(NSData *)data isBinary:(BOOL)isBinary {
@@ -86,7 +86,7 @@
 
 @implementation RTCDataChannel {
   rtc::scoped_refptr<webrtc::DataChannelInterface> _nativeDataChannel;
-  rtc::scoped_ptr<webrtc::DataChannelDelegateAdapter> _observer;
+  std::unique_ptr<webrtc::DataChannelDelegateAdapter> _observer;
   BOOL _isObserverRegistered;
 }