[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/test/rtp_file_reader.cc b/test/rtp_file_reader.cc
index 203bf30..294338a 100644
--- a/test/rtp_file_reader.cc
+++ b/test/rtp_file_reader.cc
@@ -69,15 +69,15 @@
 
 class InterleavedRtpFileReader : public RtpFileReaderImpl {
  public:
-  virtual ~InterleavedRtpFileReader() {
+  ~InterleavedRtpFileReader() override {
     if (file_ != NULL) {
       fclose(file_);
       file_ = NULL;
     }
   }
 
-  virtual bool Init(const std::string& filename,
-                    const std::set<uint32_t>& ssrc_filter) {
+  bool Init(const std::string& filename,
+            const std::set<uint32_t>& ssrc_filter) override {
     file_ = fopen(filename.c_str(), "rb");
     if (file_ == NULL) {
       printf("ERROR: Can't open file: %s\n", filename.c_str());
@@ -85,7 +85,7 @@
     }
     return true;
   }
-  virtual bool NextPacket(RtpPacket* packet) {
+  bool NextPacket(RtpPacket* packet) override {
     assert(file_ != NULL);
     packet->length = RtpPacket::kMaxPacketBufferSize;
     uint32_t len = 0;
@@ -116,7 +116,7 @@
 class RtpDumpReader : public RtpFileReaderImpl {
  public:
   RtpDumpReader() : file_(NULL) {}
-  virtual ~RtpDumpReader() {
+  ~RtpDumpReader() override {
     if (file_ != NULL) {
       fclose(file_);
       file_ = NULL;
@@ -255,7 +255,7 @@
         next_packet_it_() {
   }
 
-  virtual ~PcapReader() {
+  ~PcapReader() override {
     if (file_ != NULL) {
       fclose(file_);
       file_ = NULL;