Add method on AVFoundation capturer to adapt output format.

webrtc/sdk/objc/Framework/Classes/RTCAVFoundationVideoSource.mm

Index: webrtc/sdk/objc/Framework/Classes/RTCAVFoundationVideoSource.mm
diff --git a/webrtc/sdk/objc/Framework/Classes/RTCAVFoundationVideoSource.mm b/webrtc/sdk/objc/Framework/Classes/RTCAVFoundationVideoSource.mm
index 528e8cb62440d3a02e490ffe20b95f49b1f4ab0a..96c5c3649a4a13f9ed4f9ee2504c068d643831b6 100644
--- a/webrtc/sdk/objc/Framework/Classes/RTCAVFoundationVideoSource.mm
+++ b/webrtc/sdk/objc/Framework/Classes/RTCAVFoundationVideoSource.mm
@@ -32,6 +32,12 @@
   return [super initWithNativeVideoSource:source];
 }
 
+- (void)adaptOutputFormatToWidth:(int)width
+                          height:(int)height
+                             fps:(int)fps {
+  self.capturer->AdaptOutputFormat(width, height, fps);
+}
+
 - (BOOL)canUseBackCamera {
   return self.capturer->CanUseBackCamera();
 }