chrome: Add out-of-line copy ctors for complex classes.

chrome/browser/media/router/media_route.cc

Index: chrome/browser/media/router/media_route.cc
diff --git a/chrome/browser/media/router/media_route.cc b/chrome/browser/media/router/media_route.cc
index fb2d65e9dbfcdf9e382cd213bb0b24b47899415b..ad06280574d9267d76a236ef8b62b95093889d0a 100644
--- a/chrome/browser/media/router/media_route.cc
+++ b/chrome/browser/media/router/media_route.cc
@@ -24,6 +24,8 @@ MediaRoute::MediaRoute(const MediaRoute::Id& media_route_id,
       custom_controller_path_(custom_controller_path),
       for_display_(for_display) {}
 
+MediaRoute::MediaRoute(const MediaRoute& other) = default;
+
 MediaRoute::~MediaRoute() {
 }