Reland of Add unit tests for RTCMTLVideoView.

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

Index: webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m
diff --git a/webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m b/webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m
index 63ef23ad49433c8e136c646e33dda849d54e8ca5..427ae6c4a1138d4ca0207d8580eef61f5a8499c3 100644
--- a/webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m
+++ b/webrtc/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m
@@ -18,15 +18,18 @@
 
 #import "RTCMTLNV12Renderer.h"
 
+// To avoid unreconized symbol linker errors, we're taking advantage of the objc runtime.
+// Linking errors occur when compiling for architectures that don't support Metal.
+#define MTKViewClass NSClassFromString(@"MTKView")
+#define RTCMTLNV12RendererClass NSClassFromString(@"RTCMTLNV12Renderer")
+
 @interface RTCMTLVideoView () <MTKViewDelegate>
-@property(nonatomic, strong) id<RTCMTLRenderer> renderer;
+@property(nonatomic, strong) RTCMTLNV12Renderer *renderer;
 @property(nonatomic, strong) MTKView *metalView;
 @property(atomic, strong) RTCVideoFrame *videoFrame;
 @end
 
-@implementation RTCMTLVideoView {
-  id<RTCMTLRenderer> _renderer;
-}
+@implementation RTCMTLVideoView
 
 @synthesize renderer = _renderer;
 @synthesize metalView = _metalView;
@@ -58,11 +61,41 @@
 #endif
 }
 
++ (MTKView *)createMetalView:(CGRect)frame {
+  MTKView *view = [[MTKViewClass alloc] initWithFrame:frame];
+  return view;
+}
+
++ (RTCMTLNV12Renderer *)createMetalRenderer {
+  RTCMTLNV12Renderer *renderer = [[RTCMTLNV12RendererClass alloc] init];
+  return renderer;
+}
+
 - (void)configure {
-  if ([RTCMTLVideoView isMetalAvailable]) {
-    _metalView = [[MTKView alloc] initWithFrame:self.bounds];
+  if (![RTCMTLVideoView isMetalAvailable]) {
+    RTCLog("Metal unavailable");
+    return;
+  }
+
+  _metalView = [RTCMTLVideoView createMetalView:self.bounds];
+  _renderer = [RTCMTLVideoView createMetalRenderer];
+
+  if ([self configureMetalRenderer]) {
+    [self configureMetalView];
+  } else {
+    _renderer = nil;
+    RTCLogError("Metal configuration falied.");
+  }
+}
+
+- (BOOL)configureMetalRenderer {
+  return [_renderer addRenderingDestination:_metalView];
+}
+
+- (void)configureMetalView {
+  if (_metalView) {
+    _metalView.delegate = self;
     [self addSubview:_metalView];
-    _metalView.delegate = self;
     _metalView.contentMode = UIViewContentModeScaleAspectFit;
     _metalView.translatesAutoresizingMaskIntoConstraints = NO;
     UILayoutGuide *margins = self.layoutMarginsGuide;
@@ -70,20 +103,14 @@
     [_metalView.bottomAnchor constraintEqualToAnchor:margins.bottomAnchor].active = YES;
     [_metalView.leftAnchor constraintEqualToAnchor:margins.leftAnchor].active = YES;
     [_metalView.rightAnchor constraintEqualToAnchor:margins.rightAnchor].active = YES;
-
-    _renderer = [[RTCMTLNV12Renderer alloc] init];
-    if (![(RTCMTLNV12Renderer *)_renderer addRenderingDestination:_metalView]) {
-      _renderer = nil;
-    };
-  } else {
-    RTCLogError("Metal configuration falied.");
   }
 }
+
 #pragma mark - MTKViewDelegate methods
 
 - (void)drawInMTKView:(nonnull MTKView *)view {
   NSAssert(view == self.metalView, @"Receiving draw callbacks from foreign instance.");
-  [_renderer drawFrame:self.videoFrame];
+  [self.renderer drawFrame:self.videoFrame];
 }
 
 - (void)mtkView:(MTKView *)view drawableSizeWillChange:(CGSize)size {
@@ -92,8 +119,8 @@
 #pragma mark - RTCVideoRenderer
 
 - (void)setSize:(CGSize)size {
-  _metalView.drawableSize = size;
-  [_metalView draw];
+  self.metalView.drawableSize = size;
+  [self.metalView draw];
 }
 
 - (void)renderFrame:(nullable RTCVideoFrame *)frame {