Make MTLView content mode settable.

We want to allow the application to set it's own content mode.

Bug: b/73147161
Change-Id: I60fab454353a4c39731e49b7b6066e51d8e9a94d
Reviewed-on: https://webrtc-review.googlesource.com/70501
Commit-Queue: Kári Helgason <kthelgason@webrtc.org>
Reviewed-by: Anders Carlsson <andersc@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#22962}

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

@@ -97,6 +97,10 @@
   }
 }
 
+- (void)setVideoContentMode:(UIViewContentMode)mode {
+  _metalView.contentMode = mode;
+}
+
 #pragma mark - Private
 
 - (void)layoutSubviews {

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

@@ -32,7 +32,11 @@ NS_CLASS_AVAILABLE_IOS(9)
 
 RTC_EXPORT
 @interface RTCMTLVideoView : UIView <RTCVideoRenderer>
+
 @property(nonatomic, weak) id<RTCVideoViewDelegate> delegate;
+
+- (void)setVideoContentMode:(UIViewContentMode)mode;
+
 @end
 
 NS_ASSUME_NONNULL_END

sdk/objc/Framework/UnitTests/RTCMTLVideoView_xctest.m

@@ -11,6 +11,7 @@
 #import <XCTest/XCTest.h>
 
 #import <Foundation/Foundation.h>
+#import <MetalKit/MetalKit.h>
 #import <OCMock/OCMock.h>
 
 #include <WebRTC/RTCMTLVideoView.h>
@@ -258,4 +259,17 @@
   OCMVerifyAllWithDelay(delegateMock, 1);
 }
 
+- (void)testSetContentMode {
+  OCMStub([self.classMock isMetalAvailable]).andReturn(YES);
+  id metalKitView = OCMClassMock([MTKView class]);
+  [[[[self.classMock stub] ignoringNonObjectArgs] andReturn:metalKitView]
+      createMetalView:CGRectZero];
+  OCMExpect([metalKitView setContentMode:UIViewContentModeScaleAspectFill]);
+
+  RTCMTLVideoView *realView = [[RTCMTLVideoView alloc] init];
+  [realView setVideoContentMode:UIViewContentModeScaleAspectFill];
+
+  OCMVerify(metalKitView);
+}
+
 @end