Tweaks for new Objective-C API.

BUG=

Review URL: https://codereview.webrtc.org/1696673003

Cr-Commit-Position: refs/heads/master@{#11872}
diff --git a/webrtc/api/objc/RTCPeerConnection.mm b/webrtc/api/objc/RTCPeerConnection.mm
index f75d663..35ac07a 100644
--- a/webrtc/api/objc/RTCPeerConnection.mm
+++ b/webrtc/api/objc/RTCPeerConnection.mm
@@ -199,11 +199,11 @@
     _observer.reset(new webrtc::PeerConnectionDelegateAdapter(self));
     webrtc::PeerConnectionInterface::RTCConfiguration config =
         configuration.nativeConfiguration;
-    webrtc::MediaConstraints *nativeConstraints =
-        constraints.nativeConstraints.get();
+    rtc::scoped_ptr<webrtc::MediaConstraints> nativeConstraints =
+        constraints.nativeConstraints;
     _peerConnection =
         factory.nativeFactory->CreatePeerConnection(config,
-                                                    nativeConstraints,
+                                                    nativeConstraints.get(),
                                                     nullptr,
                                                     nullptr,
                                                     _observer.get());
@@ -259,7 +259,7 @@
 }
 
 - (void)addStream:(RTCMediaStream *)stream {
-  if (_peerConnection->AddStream(stream.nativeMediaStream)) {
+  if (!_peerConnection->AddStream(stream.nativeMediaStream)) {
     RTCLogError(@"Failed to add stream: %@", stream);
     return;
   }