Add Metal video view in AppRTCMobile and Metal availability macro.

- The RTC_SUPPORTS_METAL macro allows consumers to gracefully handle compilation for different archs that are not supporting Metal.

BUG=webrtc:7079

Review-Url: https://codereview.webrtc.org/2722583002
Cr-Commit-Position: refs/heads/master@{#17004}

webrtc/examples/objc/AppRTCMobile/ios/ARDVideoCallView.h

@@ -10,8 +10,8 @@
 
 #import <UIKit/UIKit.h>
 
-#import "WebRTC/RTCCameraPreviewView.h"
-#import "WebRTC/RTCEAGLVideoView.h"
+#import <WebRTC/RTCCameraPreviewView.h>
+#import <WebRTC/RTCVideoRenderer.h>
 
 #import "ARDStatsView.h"
 
@@ -38,7 +38,7 @@
 
 @property(nonatomic, readonly) UILabel *statusLabel;
 @property(nonatomic, readonly) RTCCameraPreviewView *localVideoView;
-@property(nonatomic, readonly) RTCEAGLVideoView *remoteVideoView;
+@property(nonatomic, readonly) __kindof UIView<RTCVideoRenderer> *remoteVideoView;
 @property(nonatomic, readonly) ARDStatsView *statsView;
 @property(nonatomic, weak) id<ARDVideoCallViewDelegate> delegate;
 

webrtc/examples/objc/AppRTCMobile/ios/ARDVideoCallView.m

@@ -11,6 +11,10 @@
 #import "ARDVideoCallView.h"
 
 #import <AVFoundation/AVFoundation.h>
+
+#import <WebRTC/RTCEAGLVideoView.h>
+#import <WebRTC/RTCMTLVideoView.h>
+
 #import "UIImage+ARDUtilities.h"
 
 static CGFloat const kButtonPadding = 16;
@@ -38,8 +42,15 @@ static CGFloat const kStatusBarHeight = 20;
 
 - (instancetype)initWithFrame:(CGRect)frame {
   if (self = [super initWithFrame:frame]) {
-    _remoteVideoView = [[RTCEAGLVideoView alloc] initWithFrame:CGRectZero];
-    _remoteVideoView.delegate = self;
+
+#if defined(RTC_SUPPORTS_METAL)
+    _remoteVideoView = [[RTCMTLVideoView alloc] initWithFrame:CGRectZero];
+#else
+    RTCEAGLVideoView *remoteView = [[RTCEAGLVideoView alloc] initWithFrame:CGRectZero];
+    remoteView.delegate = self;
+    _remoteVideoView = remoteView;
+#endif
+
     [self addSubview:_remoteVideoView];
 
     _localVideoView = [[RTCCameraPreviewView alloc] initWithFrame:CGRectZero];

webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m

@@ -51,9 +51,9 @@
 #pragma mark - Private
 
 + (BOOL)isMetalAvailable {
-#if defined(__OBJC__) && COREVIDEO_SUPPORTS_METAL
+#if defined(RTC_SUPPORTS_METAL)
   return YES;
-#elif
+#else
   return NO;
 #endif
 }

webrtc/sdk/objc/Framework/Headers/WebRTC/RTCMTLVideoView.h

@@ -12,8 +12,13 @@
 
 #import "WebRTC/RTCVideoRenderer.h"
 
+// Check if metal is supported in WebRTC.
+// NOTE: Currently arm64 == Metal.
+#if defined(__aarch64__)
+#define RTC_SUPPORTS_METAL
+#endif
+
 NS_ASSUME_NONNULL_BEGIN
-RTC_EXPORT
 
 /**
  * RTCMTLVideoView is thin wrapper around MTKView.
@@ -22,6 +27,8 @@ RTC_EXPORT
  * bounds using Metal.
  */
 NS_CLASS_AVAILABLE_IOS(9)
+
+RTC_EXPORT
 @interface RTCMTLVideoView : UIView <RTCVideoRenderer>
 
 @end