Polishing code to handle certificate generation failure in .mm files.

This is a follow-up to https://codereview.webrtc.org/1965313002/ which
was TBR-landed.

Minor code clean-up/corrections:

Property nativeConfiguration -> - method createNativeConfiguration.
RTCLogWarning -> RTCLogError.
setConfiguration returning NO instead of false.
initWithFactory returning nil instead of nullptr.
Braces around ifs.

Review-Url: https://codereview.webrtc.org/1978233002
Cr-Commit-Position: refs/heads/master@{#12770}

webrtc/sdk/objc/Framework/Classes/RTCConfiguration+Private.h

@@ -16,13 +16,6 @@ NS_ASSUME_NONNULL_BEGIN
 
 @interface RTCConfiguration ()
 
-/**
- * RTCConfiguration struct representation of this RTCConfiguration. This is
- * needed to pass to the underlying C++ APIs.
- */
-@property(nonatomic, readonly)
-    webrtc::PeerConnectionInterface::RTCConfiguration* nativeConfiguration;
-
 + (webrtc::PeerConnectionInterface::IceTransportsType)
     nativeTransportsTypeForTransportPolicy:(RTCIceTransportPolicy)policy;
 
@@ -55,6 +48,13 @@ NS_ASSUME_NONNULL_BEGIN
 
 + (NSString *)stringForTcpCandidatePolicy:(RTCTcpCandidatePolicy)policy;
 
+/**
+ * RTCConfiguration struct representation of this RTCConfiguration. This is
+ * needed to pass to the underlying C++ APIs.
+ */
+- (webrtc::PeerConnectionInterface::RTCConfiguration *)
+    createNativeConfiguration;
+
 @end
 
 NS_ASSUME_NONNULL_END

webrtc/sdk/objc/Framework/Classes/RTCConfiguration.mm

@@ -75,7 +75,8 @@
 
 #pragma mark - Private
 
-- (webrtc::PeerConnectionInterface::RTCConfiguration*)nativeConfiguration {
+- (webrtc::PeerConnectionInterface::RTCConfiguration *)
+    createNativeConfiguration {
   std::unique_ptr<webrtc::PeerConnectionInterface::RTCConfiguration>
       nativeConfig(new webrtc::PeerConnectionInterface::RTCConfiguration());
 
@@ -105,7 +106,7 @@
         rtc::RTCCertificateGenerator::GenerateCertificate(
             rtc::KeyParams(keyType), rtc::Optional<uint64_t>());
     if (!certificate) {
-      RTCLogWarning(@"Failed to generate certificate.");
+      RTCLogError(@"Failed to generate certificate.");
       return nullptr;
     }
     nativeConfig->certificates.push_back(certificate);

webrtc/sdk/objc/Framework/Classes/RTCPeerConnection.mm

@@ -199,9 +199,10 @@ void PeerConnectionDelegateAdapter::OnIceCandidate(
                        delegate:(id<RTCPeerConnectionDelegate>)delegate {
   NSParameterAssert(factory);
   std::unique_ptr<webrtc::PeerConnectionInterface::RTCConfiguration> config(
-      configuration.nativeConfiguration);
-  if (!config)
-    return nullptr;
+      [configuration createNativeConfiguration]);
+  if (!config) {
+    return nil;
+  }
   if (self = [super init]) {
     _observer.reset(new webrtc::PeerConnectionDelegateAdapter(self));
     std::unique_ptr<webrtc::MediaConstraints> nativeConstraints =
@@ -255,9 +256,10 @@ void PeerConnectionDelegateAdapter::OnIceCandidate(
 
 - (BOOL)setConfiguration:(RTCConfiguration *)configuration {
   std::unique_ptr<webrtc::PeerConnectionInterface::RTCConfiguration> config(
-      configuration.nativeConfiguration);
-  if (!config)
-    return false;
+      [configuration createNativeConfiguration]);
+  if (!config) {
+    return NO;
+  }
   return _peerConnection->SetConfiguration(*config);
 }