Add defaulted move constructors for some types that just got copy constructors

webrtc/base/pathutils.cc

Index: webrtc/base/pathutils.cc
diff --git a/webrtc/base/pathutils.cc b/webrtc/base/pathutils.cc
index 60e2b8bf47e51d6ffd0e9db7a8d04a68f0f9eb8d..a420eb5136af9134752c250556fe62164db78f7e 100644
--- a/webrtc/base/pathutils.cc
+++ b/webrtc/base/pathutils.cc
@@ -56,6 +56,7 @@ Pathname::Pathname()
 }
 
 Pathname::Pathname(const Pathname&) = default;
+Pathname::Pathname(Pathname&&) = default;
 
 Pathname::Pathname(const std::string& pathname)
     : folder_delimiter_(DEFAULT_FOLDER_DELIM) {
@@ -67,6 +68,9 @@ Pathname::Pathname(const std::string& folder, const std::string& filename)
   SetPathname(folder, filename);
 }
 
+Pathname& Pathname::operator=(const Pathname&) = default;
+Pathname& Pathname::operator=(Pathname&&) = default;
+
 void Pathname::SetFolderDelimiter(char delimiter) {
   ASSERT(IsFolderDelimiter(delimiter));
   folder_delimiter_ = delimiter;