Avoid needless container and scoped_refptr copies

Several call sites deep-copy Codec, Candidate and logged RTP stream
objects, or whole vectors of them, that they only read. A few
constructors also copy by-value scoped_refptr parameters instead of
moving them.

- Bind getter results and loop elements by const reference: the codec
  lists in the SDP munging detector and in CodecList's AbslStringify,
  the port candidates in GetCandidateStatsFromReadyPorts, and the logged
  RTP streams in the NetEq event log input.
- Move by-value scoped_refptr parameters into their members in the
  PeerConnection, BroadcastResourceListener and
  ResourceVideoSendStreamForwarder constructors.

Bug: webrtc:374845009
Change-Id: I7f213313c894252896ccd3f39c03f455d5e84566
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/498621
Reviewed-by: Tomas Gunnarsson <tommi@webrtc.org>
Commit-Queue: Fredrik Solenberg <solenberg@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#48805}

call/adaptation/broadcast_resource_listener.cc

diff --git a/call/adaptation/broadcast_resource_listener.cc b/call/adaptation/broadcast_resource_listener.cc
index 5305964..2a9c447 100644
--- a/call/adaptation/broadcast_resource_listener.cc
+++ b/call/adaptation/broadcast_resource_listener.cc
@@ -57,7 +57,7 @@
 
 BroadcastResourceListener::BroadcastResourceListener(
     scoped_refptr<Resource> source_resource)
-    : source_resource_(source_resource), is_listening_(false) {
+    : source_resource_(std::move(source_resource)), is_listening_(false) {
   RTC_DCHECK(source_resource_);
 }
 

call/call.cc

diff --git a/call/call.cc b/call/call.cc
index 6ce9c7f..a848c64 100644
--- a/call/call.cc
+++ b/call/call.cc
@@ -167,7 +167,7 @@
  public:
   explicit ResourceVideoSendStreamForwarder(
       scoped_refptr<webrtc::Resource> resource)
-      : broadcast_resource_listener_(resource) {
+      : broadcast_resource_listener_(std::move(resource)) {
     broadcast_resource_listener_.StartListening();
   }
   ~ResourceVideoSendStreamForwarder() {

media/base/codec_list.h

diff --git a/media/base/codec_list.h b/media/base/codec_list.h
index 6f87f90..021fde2 100644
--- a/media/base/codec_list.h
+++ b/media/base/codec_list.h
@@ -100,7 +100,7 @@
   template <typename Sink>
   friend void AbslStringify(Sink& sink, const CodecList& list) {
     absl::Format(&sink, "\n--- Codec list of size %d\n", list.size());
-    for (Codec codec : list) {
+    for (const Codec& codec : list) {
       absl::Format(&sink, "%v\n", codec);
     }
     sink.Append("--- End\n");

modules/audio_coding/neteq/tools/neteq_event_log_input.cc

diff --git a/modules/audio_coding/neteq/tools/neteq_event_log_input.cc b/modules/audio_coding/neteq/tools/neteq_event_log_input.cc
index f7834c6..27a617a 100644
--- a/modules/audio_coding/neteq/tools/neteq_event_log_input.cc
+++ b/modules/audio_coding/neteq/tools/neteq_event_log_input.cc
@@ -163,10 +163,10 @@
   }
   // Pick the first SSRC if none was provided.
   ssrc = ssrc.value_or(*parsed_log.incoming_audio_ssrcs().begin());
-  auto streams = parsed_log.incoming_rtp_packets_by_ssrc();
+  const auto& streams = parsed_log.incoming_rtp_packets_by_ssrc();
   auto stream =
       std::find_if(streams.begin(), streams.end(),
-                   [ssrc](auto stream) { return stream.ssrc == ssrc; });
+                   [ssrc](const auto& stream) { return stream.ssrc == ssrc; });
   if (stream == streams.end()) {
     return nullptr;
   }

p2p/client/basic_port_allocator.cc

diff --git a/p2p/client/basic_port_allocator.cc b/p2p/client/basic_port_allocator.cc
index 1950d73..15cca3b 100644
--- a/p2p/client/basic_port_allocator.cc
+++ b/p2p/client/basic_port_allocator.cc
@@ -477,7 +477,7 @@
     CandidateStatsList* candidate_stats_list) const {
   auto ports = ReadyPorts();
   for (auto* port : ports) {
-    auto candidates = port->Candidates();
+    const auto& candidates = port->Candidates();
     for (const auto& candidate : candidates) {
       std::optional<StunStats> stun_stats;
       port->GetStunStats(&stun_stats);

pc/peer_connection.cc

diff --git a/pc/peer_connection.cc b/pc/peer_connection.cc
index 15a0e4e..10e6ff9 100644
--- a/pc/peer_connection.cc
+++ b/pc/peer_connection.cc
@@ -471,7 +471,7 @@
     const std::vector<RelayServerConfig>& turn_servers,
     bool dtls_enabled)
     : env_(env),
-      context_(context),
+      context_(std::move(context)),
       options_(options),
       observer_(dependencies.observer),
       is_unified_plan_(is_unified_plan),

pc/sdp_munging_detector.cc

diff --git a/pc/sdp_munging_detector.cc b/pc/sdp_munging_detector.cc
index bed58ed..31129d2 100644
--- a/pc/sdp_munging_detector.cc
+++ b/pc/sdp_munging_detector.cc
@@ -310,8 +310,8 @@
   MediaType media_type = last_created_media_description->type();
   // Validate codecs. We should have bailed out earlier if codecs were added
   // or removed.
-  auto last_created_codecs = last_created_media_description->codecs();
-  auto codecs_to_set = media_description_to_set->codecs();
+  const auto& last_created_codecs = last_created_media_description->codecs();
+  const auto& codecs_to_set = media_description_to_set->codecs();
   if (last_created_codecs.size() == codecs_to_set.size()) {
     for (size_t i = 0; i < last_created_codecs.size(); i++) {
       if (last_created_codecs[i] == codecs_to_set[i]) {