Add explicit copy constructors to RTPHeader and RTPHeaderExtension

Explicit copy-constructors are required by chromium. (No copy constructors were used until now, but a different CL requires them.)

BUG=None
TBR=stefan@webrtc.org

Review-Url: https://codereview.webrtc.org/3006343002
Cr-Original-Commit-Position: refs/heads/master@{#19777}
Cr-Mirrored-From: https://chromium.googlesource.com/external/webrtc
Cr-Mirrored-Commit: 98b1b7d59e5b9eab61211d3b13dab87cb3bb18ce
diff --git a/common_types.cc b/common_types.cc
index 82307ce..1ea4099 100644
--- a/common_types.cc
+++ b/common_types.cc
@@ -57,6 +57,12 @@
       videoContentType(VideoContentType::UNSPECIFIED),
       has_video_timing(false) {}
 
+RTPHeaderExtension::RTPHeaderExtension(const RTPHeaderExtension& other) =
+    default;
+
+RTPHeaderExtension& RTPHeaderExtension::operator=(
+    const RTPHeaderExtension& other) = default;
+
 RTPHeader::RTPHeader()
     : markerBit(false),
       payloadType(0),
@@ -70,6 +76,10 @@
       payload_type_frequency(0),
       extension() {}
 
+RTPHeader::RTPHeader(const RTPHeader& other) = default;
+
+RTPHeader& RTPHeader::operator=(const RTPHeader& other) = default;
+
 VideoCodec::VideoCodec()
     : codecType(kVideoCodecUnknown),
       plName(),
diff --git a/common_types.h b/common_types.h
index 49b42ac..e5bd9a8 100644
--- a/common_types.h
+++ b/common_types.h
@@ -792,6 +792,8 @@
 
 struct RTPHeaderExtension {
   RTPHeaderExtension();
+  RTPHeaderExtension(const RTPHeaderExtension& other);
+  RTPHeaderExtension& operator=(const RTPHeaderExtension& other);
 
   bool hasTransmissionTimeOffset;
   int32_t transmissionTimeOffset;
@@ -835,6 +837,8 @@
 
 struct RTPHeader {
   RTPHeader();
+  RTPHeader(const RTPHeader& other);
+  RTPHeader& operator=(const RTPHeader& other);
 
   bool markerBit;
   uint8_t payloadType;