Reland of Add Metal video view in AppRTCMobile and metal availability macro. (patchset #1 id:1 of https://codereview.webrtc.org/2739793003/ )

Reason for revert:
Fixing rendering issues in AppRTCMobile

Original issue's description:
> Revert of Add Metal video view in AppRTCMobile and metal availability macro. (patchset #5 id:80001 of https://codereview.webrtc.org/2722583002/ )
>
> Reason for revert:
> Breaks AppRTCMobile
>
> Original issue's description:
> > 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}
> > Committed: 154a7bb877
>
> TBR=magjed@webrtc.org,tkchin@webrtc.org,denicija@webrtc.org
> # Not skipping CQ checks because original CL landed more than 1 days ago.
> BUG=webrtc:7079
>
> Review-Url: https://codereview.webrtc.org/2739793003
> Cr-Commit-Position: refs/heads/master@{#17119}
> Committed: cbbd8c76e8

TBR=magjed@webrtc.org,tkchin@webrtc.org,denicija@webrtc.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=webrtc:7079

Review-Url: https://codereview.webrtc.org/2742603003
Cr-Commit-Position: refs/heads/master@{#17139}

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/RTCMTLNV12Renderer.mm

@@ -239,10 +239,10 @@ static const NSInteger kMaxInflightBuffers = 1;
     dispatch_semaphore_signal(block_semaphore);
   }];
 
-  MTLRenderPassDescriptor *_renderPassDescriptor = _view.currentRenderPassDescriptor;
-  if (_renderPassDescriptor) {  // Valid drawable.
+  MTLRenderPassDescriptor *renderPassDescriptor = _view.currentRenderPassDescriptor;
+  if (renderPassDescriptor) {  // Valid drawable.
     id<MTLRenderCommandEncoder> renderEncoder =
-        [commandBuffer renderCommandEncoderWithDescriptor:_renderPassDescriptor];
+        [commandBuffer renderCommandEncoderWithDescriptor:renderPassDescriptor];
     renderEncoder.label = renderEncoderLabel;
 
     // Set context state.
@@ -269,13 +269,13 @@ static const NSInteger kMaxInflightBuffers = 1;
 #pragma mark - RTCMTLRenderer
 
 - (void)drawFrame:(RTCVideoFrame *)frame {
-  [self setupTexturesForFrame:frame];
   @autoreleasepool {
-    [self render];
+    if ([self setupTexturesForFrame:frame])
+      [self render];
   }
 }
 
-- (void)setupTexturesForFrame:(nonnull RTCVideoFrame *)frame {
+- (BOOL)setupTexturesForFrame:(nonnull RTCVideoFrame *)frame {
   CVPixelBufferRef pixelBuffer = frame.nativeHandle;
 
   id<MTLTexture> lumaTexture = nil;
@@ -313,7 +313,9 @@ static const NSInteger kMaxInflightBuffers = 1;
     _yTexture = lumaTexture;
     _CrCbTexture = chromaTexture;
     _offset = offsetForRotation((webrtc::VideoRotation)frame.rotation);
+    return YES;
   }
+  return NO;
 }
 
 @end

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