Return a copy of the supported RTP header extensions instead of a reference.

talk/media/webrtc/webrtcvoiceengine.cc

Index: talk/media/webrtc/webrtcvoiceengine.cc
diff --git a/talk/media/webrtc/webrtcvoiceengine.cc b/talk/media/webrtc/webrtcvoiceengine.cc
index 4bd0400dfa8e394642f22a65f77a601b7efec2f7..bd4c47d15bc2d70364e8ac63e934cfe7e9117815 100644
--- a/talk/media/webrtc/webrtcvoiceengine.cc
+++ b/talk/media/webrtc/webrtcvoiceengine.cc
@@ -524,18 +524,6 @@ void WebRtcVoiceEngine::Construct() {
   // Load our audio codec list.
   codecs_ = WebRtcVoiceCodecs::SupportedCodecs();
 
-  // Load our RTP Header extensions.
-  rtp_header_extensions_.push_back(
-      RtpHeaderExtension(kRtpAudioLevelHeaderExtension,
-                         kRtpAudioLevelHeaderExtensionDefaultId));
-  rtp_header_extensions_.push_back(
-      RtpHeaderExtension(kRtpAbsoluteSenderTimeHeaderExtension,
-                         kRtpAbsoluteSenderTimeHeaderExtensionDefaultId));
-  if (webrtc::field_trial::FindFullName("WebRTC-SendSideBwe") == "Enabled") {
-    rtp_header_extensions_.push_back(RtpHeaderExtension(
-        kRtpTransportSequenceNumberHeaderExtension,
-        kRtpTransportSequenceNumberHeaderExtensionDefaultId));
-  }
   options_ = GetDefaultEngineOptions();
 }
 
@@ -1097,10 +1085,21 @@ const std::vector<AudioCodec>& WebRtcVoiceEngine::codecs() {
   return codecs_;
 }
 
-const std::vector<RtpHeaderExtension>&
-WebRtcVoiceEngine::rtp_header_extensions() const {
+std::vector<RtpHeaderExtension>
+WebRtcVoiceEngine::SupportedRtpHeaderExtensions() const {
   RTC_DCHECK(signal_thread_checker_.CalledOnValidThread());
-  return rtp_header_extensions_;
+  std::vector<RtpHeaderExtension> rtp_header_extensions;
+  rtp_header_extensions.push_back(RtpHeaderExtension(
+      kRtpAudioLevelHeaderExtension, kRtpAudioLevelHeaderExtensionDefaultId));
+  rtp_header_extensions.push_back(
+      RtpHeaderExtension(kRtpAbsoluteSenderTimeHeaderExtension,
+                         kRtpAbsoluteSenderTimeHeaderExtensionDefaultId));
+  if (webrtc::field_trial::FindFullName("WebRTC-SendSideBwe") == "Enabled") {
+    rtp_header_extensions.push_back(RtpHeaderExtension(
+        kRtpTransportSequenceNumberHeaderExtension,
+        kRtpTransportSequenceNumberHeaderExtensionDefaultId));
+  }
+  return rtp_header_extensions;
 }
 
 int WebRtcVoiceEngine::GetLastEngineError() {