Add runtime check for metal support.

Bug: None
Change-Id: I1bc64c072c3ccf3430e084f9598931c159e6b039
Reviewed-on: https://webrtc-review.googlesource.com/70800
Reviewed-by: Peter Hanspers <peterhanspers@webrtc.org>
Commit-Queue: Kári Helgason <kthelgason@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#23072}
diff --git a/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m b/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m
index bef3b6a..9ec2583 100644
--- a/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m
+++ b/sdk/objc/Framework/Classes/Metal/RTCMTLVideoView.m
@@ -64,7 +64,7 @@
 
 + (BOOL)isMetalAvailable {
 #if defined(RTC_SUPPORTS_METAL)
-  return YES;
+  return MTLCreateSystemDefaultDevice() != nil;
 #else
   return NO;
 #endif