iOS/MacOS:Refactor metal rendering by extracting common implementation

webrtc/examples/objc/AppRTCMobile/mac/APPRTCViewController.m

 /*
  *  Copyright 2014 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.
  */
 
@@ skipping 197 matching lines @@
   [_logView setEditable:NO];
 
   [self setupActionItemsView];
 
   _scrollView = [[NSScrollView alloc] initWithFrame:NSZeroRect];
   [_scrollView setTranslatesAutoresizingMaskIntoConstraints:NO];
   [_scrollView setHasVerticalScroller:YES];
   [_scrollView setDocumentView:_logView];
   [self addSubview:_scrollView];
 
-
 // NOTE (daniela): Ignoring Clang diagonstic here.
 // We're performing run time check to make sure class is available on runtime.
 // If not we're providing sensible default.
 #pragma clang diagnostic push
 #pragma clang diagnostic ignored "-Wpartial-availability"
   if ([RTCMTLNSVideoView class]) {
     _remoteVideoView = [[RTCMTLNSVideoView alloc] initWithFrame:NSZeroRect];
     _localVideoView = [[RTCMTLNSVideoView alloc] initWithFrame:NSZeroRect];
   } else {
     NSOpenGLPixelFormatAttribute attributes[] = {
@@ skipping 188 matching lines @@
   [self.mainView.remoteVideoView renderFrame:nil];
   [self.mainView.localVideoView renderFrame:nil];
 }
 
 - (void)disconnect {
   [self resetUI];
   [_client disconnect];
 }
 
 @end