Added OnResolutionChange to EncoderSelectorInterface.

Bug: webrtc:12406
Change-Id: I0160636d93ad0a33caf7ae7443cefe321a191406
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/258442
Reviewed-by: Sergey Silkin <ssilkin@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Commit-Queue: Philip Eliasson <philipel@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#36517}

api/video_codecs/video_encoder_factory.h

@@ -17,6 +17,7 @@
 
 #include "absl/types/optional.h"
 #include "api/units/data_rate.h"
+#include "api/video/render_resolution.h"
 #include "api/video_codecs/sdp_video_format.h"
 
 namespace webrtc {
@@ -47,6 +48,13 @@ class VideoEncoderFactory {
     virtual absl::optional<SdpVideoFormat> OnAvailableBitrate(
         const DataRate& rate) = 0;
 
+    // Called every time the encoder input resolution change. Should return a
+    // non-empty if an encoder switch should be performed.
+    virtual absl::optional<SdpVideoFormat> OnResolutionChange(
+        const RenderResolution& resolution) {
+      return absl::nullopt;
+    }
+
     // Called if the currently used encoder reports itself as broken. Should
     // return a non-empty if an encoder switch should be performed.
     virtual absl::optional<SdpVideoFormat> OnEncoderBroken() = 0;