Implement OnResolutionChange to objc RTCVideoEncoderSelector

Bug: webrtc:12406
Change-Id: I3335d895ecd207ba9de92397cffa3b80799df4ad
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/258700
Reviewed-by: Kári Helgason <kthelgason@webrtc.org>
Commit-Queue: Daniel.L (Byoungchan) Lee <daniel.l@hpcnt.com>
Cr-Commit-Position: refs/heads/main@{#36589}
diff --git a/sdk/objc/base/RTCVideoEncoderFactory.h b/sdk/objc/base/RTCVideoEncoderFactory.h
index b115b2a..a73cd77 100644
--- a/sdk/objc/base/RTCVideoEncoderFactory.h
+++ b/sdk/objc/base/RTCVideoEncoderFactory.h
@@ -27,6 +27,9 @@
 - (nullable RTC_OBJC_TYPE(RTCVideoCodecInfo) *)encoderForBitrate:(NSInteger)bitrate;
 - (nullable RTC_OBJC_TYPE(RTCVideoCodecInfo) *)encoderForBrokenEncoder;
 
+@optional
+- (nullable RTC_OBJC_TYPE(RTCVideoCodecInfo) *)encoderForResolutionChangeBySize:(CGSize)size;
+
 @end
 
 /** RTCVideoEncoderFactory is an Objective-C version of webrtc::VideoEncoderFactory.