Update API for Objective-C RTCPeerConnectionFactory.

BUG=
R=jiayl@webrtc.org, tkchin@webrtc.org

Review URL: https://codereview.webrtc.org/1558473002 .

Patch from Jon Hjelle <hjon@andyet.net>.

Cr-Commit-Position: refs/heads/master@{#11326}
diff --git a/webrtc/api/api.gyp b/webrtc/api/api.gyp
index 87f90d9..f957f5b 100644
--- a/webrtc/api/api.gyp
+++ b/webrtc/api/api.gyp
@@ -33,6 +33,9 @@
             'objc/RTCMediaStreamTrack.mm',
             'objc/RTCOpenGLVideoRenderer.h',
             'objc/RTCOpenGLVideoRenderer.mm',
+            'objc/RTCPeerConnectionFactory+Private.h',
+            'objc/RTCPeerConnectionFactory.h',
+            'objc/RTCPeerConnectionFactory.mm',
             'objc/RTCSessionDescription+Private.h',
             'objc/RTCSessionDescription.h',
             'objc/RTCSessionDescription.mm',