Adding codecs to the RtpParameters returned by an RtpSender.

Contains every field except for sdpFmtpLine.
Setting a reordered list of codecs is not yet supported.

R=glaznev@webrtc.org, pthatcher@webrtc.org, skvlad@webrtc.org, tkchin@webrtc.org

Review URL: https://codereview.webrtc.org/1885473004 .

Cr-Commit-Position: refs/heads/master@{#12453}
diff --git a/webrtc/api/objc/RTCRtpCodecParameters.mm b/webrtc/api/objc/RTCRtpCodecParameters.mm
new file mode 100644
index 0000000..8bc2204
--- /dev/null
+++ b/webrtc/api/objc/RTCRtpCodecParameters.mm
@@ -0,0 +1,63 @@
+/*
+ *  Copyright 2016 The WebRTC project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#import "RTCRtpCodecParameters+Private.h"
+
+#import "webrtc/base/objc/NSString+StdString.h"
+#import "webrtc/media/base/mediaconstants.h"
+
+const NSString * const kRtxCodecMimeType = @(cricket::kRtxCodecName);
+const NSString * const kRedCodecMimeType = @(cricket::kRedCodecName);
+const NSString * const kUlpfecCodecMimeType = @(cricket::kUlpfecCodecName);
+const NSString * const kOpusCodecMimeType = @(cricket::kOpusCodecName);
+const NSString * const kIsacCodecMimeType = @(cricket::kIsacCodecName);
+const NSString * const kL16CodecMimeType  = @(cricket::kL16CodecName);
+const NSString * const kG722CodecMimeType = @(cricket::kG722CodecName);
+const NSString * const kIlbcCodecMimeType = @(cricket::kIlbcCodecName);
+const NSString * const kPcmuCodecMimeType = @(cricket::kPcmuCodecName);
+const NSString * const kPcmaCodecMimeType = @(cricket::kPcmaCodecName);
+const NSString * const kDtmfCodecMimeType = @(cricket::kDtmfCodecName);
+const NSString * const kComfortNoiseCodecMimeType = @(cricket::kComfortNoiseCodecName);
+const NSString * const kVp8CodecMimeType = @(cricket::kVp8CodecName);
+const NSString * const kVp9CodecMimeType = @(cricket::kVp9CodecName);
+const NSString * const kH264CodecMimeType = @(cricket::kH264CodecName);
+
+@implementation RTCRtpCodecParameters
+
+@synthesize payloadType = _payloadType;
+@synthesize mimeType = _mimeType;
+@synthesize clockRate = _clockRate;
+@synthesize channels = _channels;
+
+- (instancetype)init {
+  return [super init];
+}
+
+- (instancetype)initWithNativeParameters:
+    (const webrtc::RtpCodecParameters &)nativeParameters {
+  if (self = [self init]) {
+    _payloadType = nativeParameters.payload_type;
+    _mimeType = [NSString stringForStdString:nativeParameters.mime_type];
+    _clockRate = nativeParameters.clock_rate;
+    _channels = nativeParameters.channels;
+  }
+  return self;
+}
+
+- (webrtc::RtpCodecParameters)nativeParameters {
+  webrtc::RtpCodecParameters parameters;
+  parameters.payload_type = _payloadType;
+  parameters.mime_type = [NSString stdStringForString:_mimeType];
+  parameters.clock_rate = _clockRate;
+  parameters.channels = _channels;
+  return parameters;
+}
+
+@end