Replace use of codec name strings with constants.

Bug: webrtc:8401
Change-Id: I2aee61e026330ec233eb8b3bfe2d529187562249
Reviewed-on: https://webrtc-review.googlesource.com/10814
Reviewed-by: Magnus Jedvert <magjed@webrtc.org>
Commit-Queue: Kári Helgason <kthelgason@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#20340}
diff --git a/sdk/objc/Framework/Classes/PeerConnection/RTCVideoCodec.mm b/sdk/objc/Framework/Classes/PeerConnection/RTCVideoCodec.mm
index 46e6a51..2a49189 100644
--- a/sdk/objc/Framework/Classes/PeerConnection/RTCVideoCodec.mm
+++ b/sdk/objc/Framework/Classes/PeerConnection/RTCVideoCodec.mm
@@ -14,6 +14,12 @@
 #import "RTCVideoCodec+Private.h"
 #import "WebRTC/RTCVideoCodecFactory.h"
 
+NSString *const kVideoCodecVp8Name = @"VP8";
+NSString *const kVideoCodecVp9Name = @"VP9";
+NSString *const kVideoCodecH264Name = @"H264";
+NSString *const kLevel31ConstrainedHigh = @"640c1f";
+NSString *const kLevel31ConstrainedBaseline = @"42e01f";
+
 @implementation RTCVideoCodecInfo
 
 @synthesize name = _name;