[iOS] Added an initialization method to RTCConfiguration that takes a
native configuration.
Added a getConfiguration getter method to RTCPeerConnection to return
the RTCConfiguration.

BUG=webrtc:7431

Review-Url: https://codereview.webrtc.org/2790833002
Cr-Commit-Position: refs/heads/master@{#17517}
diff --git a/webrtc/sdk/BUILD.gn b/webrtc/sdk/BUILD.gn
index 644a94f..d8e745c 100644
--- a/webrtc/sdk/BUILD.gn
+++ b/webrtc/sdk/BUILD.gn
@@ -268,6 +268,7 @@
         "objc/Framework/UnitTests/RTCIceCandidateTest.mm",
         "objc/Framework/UnitTests/RTCIceServerTest.mm",
         "objc/Framework/UnitTests/RTCMediaConstraintsTest.mm",
+        "objc/Framework/UnitTests/RTCPeerConnectionTest.mm",
         "objc/Framework/UnitTests/RTCSessionDescriptionTest.mm",
         "objc/Framework/UnitTests/avformatmappertests.mm",
       ]