[clang-tidy] Apply modernize-use-override fixes.

This CL applies clang-tidy's modernize-use-override [1] to the
WebRTC codebase.

All changes in this CL are automatically generated by both clang-tidy
and 'git cl format'.

[1] - https://clang.llvm.org/extra/clang-tidy/checks/modernize-use-override.html

Bug: webrtc:10252
Change-Id: I2bb8bd90fa8adb90aa33861fe7c788132a819a20
Reviewed-on: https://webrtc-review.googlesource.com/c/120412
Reviewed-by: Karl Wiberg <kwiberg@webrtc.org>
Commit-Queue: Mirko Bonadei <mbonadei@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#26461}
diff --git a/modules/video_coding/utility/simulcast_test_fixture_impl.cc b/modules/video_coding/utility/simulcast_test_fixture_impl.cc
index 781c7d0..c65941a 100644
--- a/modules/video_coding/utility/simulcast_test_fixture_impl.cc
+++ b/modules/video_coding/utility/simulcast_test_fixture_impl.cc
@@ -70,14 +70,14 @@
     memset(layer_sync_, false, sizeof(layer_sync_));
   }
 
-  ~TestEncodedImageCallback() {
+  ~TestEncodedImageCallback() override {
     delete[] encoded_key_frame_.data();
     delete[] encoded_frame_.data();
   }
 
-  virtual Result OnEncodedImage(const EncodedImage& encoded_image,
-                                const CodecSpecificInfo* codec_specific_info,
-                                const RTPFragmentationHeader* fragmentation) {
+  Result OnEncodedImage(const EncodedImage& encoded_image,
+                        const CodecSpecificInfo* codec_specific_info,
+                        const RTPFragmentationHeader* fragmentation) override {
     bool is_vp8 = (codec_specific_info->codecType == kVideoCodecVP8);
     // Only store the base layer.
     if (encoded_image.SpatialIndex().value_or(0) == 0) {
diff --git a/modules/video_coding/video_coding_impl.cc b/modules/video_coding/video_coding_impl.cc
index 9796e8c..2c1d898 100644
--- a/modules/video_coding/video_coding_impl.cc
+++ b/modules/video_coding/video_coding_impl.cc
@@ -50,7 +50,7 @@
         timing_(new VCMTiming(clock)),
         receiver_(clock, timing_.get(), nack_sender, keyframe_request_sender) {}
 
-  virtual ~VideoCodingModuleImpl() {}
+  ~VideoCodingModuleImpl() override {}
 
   int64_t TimeUntilNextProcess() override {
     int64_t receiver_time = receiver_.TimeUntilNextProcess();