Split iOS sdk in to separate targets

This CL splits the iOS sdk into separate static libraries for video,
audio, ui, common, and peerconnection-related code. This will in the
future make it easier to compile WebRTC without unneeded components.

BUG=webrtc:4867

Review-Url: https://codereview.webrtc.org/2862543002
Cr-Commit-Position: refs/heads/master@{#18166}

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

@@ -1,66 +0,0 @@
-/*
- *  Copyright 2015 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 "RTCAudioTrack+Private.h"
-
-#import "NSString+StdString.h"
-#import "RTCAudioSource+Private.h"
-#import "RTCMediaStreamTrack+Private.h"
-#import "RTCPeerConnectionFactory+Private.h"
-
-#include "webrtc/base/checks.h"
-
-@implementation RTCAudioTrack
-
-@synthesize source = _source;
-
-- (instancetype)initWithFactory:(RTCPeerConnectionFactory *)factory
-                         source:(RTCAudioSource *)source
-                        trackId:(NSString *)trackId {
-  RTC_DCHECK(factory);
-  RTC_DCHECK(source);
-  RTC_DCHECK(trackId.length);
-
-  std::string nativeId = [NSString stdStringForString:trackId];
-  rtc::scoped_refptr<webrtc::AudioTrackInterface> track =
-      factory.nativeFactory->CreateAudioTrack(nativeId, source.nativeAudioSource);
-  if ([self initWithNativeTrack:track type:RTCMediaStreamTrackTypeAudio]) {
-    _source = source;
-  }
-  return self;
-}
-
-- (instancetype)initWithNativeTrack:
-    (rtc::scoped_refptr<webrtc::MediaStreamTrackInterface>)nativeTrack
-                               type:(RTCMediaStreamTrackType)type {
-  NSParameterAssert(nativeTrack);
-  NSParameterAssert(type == RTCMediaStreamTrackTypeAudio);
-  return [super initWithNativeTrack:nativeTrack type:type];
-}
-
-
-- (RTCAudioSource *)source {
-  if (!_source) {
-    rtc::scoped_refptr<webrtc::AudioSourceInterface> source =
-        self.nativeAudioTrack->GetSource();
-    if (source) {
-      _source = [[RTCAudioSource alloc] initWithNativeAudioSource:source.get()];
-    }
-  }
-  return _source;
-}
-
-#pragma mark - Private
-
-- (rtc::scoped_refptr<webrtc::AudioTrackInterface>)nativeAudioTrack {
-  return static_cast<webrtc::AudioTrackInterface *>(self.nativeTrack.get());
-}
-
-@end