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

chrome/test/chromedriver/server/http_handler.cc

Index: chrome/test/chromedriver/server/http_handler.cc
diff --git a/chrome/test/chromedriver/server/http_handler.cc b/chrome/test/chromedriver/server/http_handler.cc
index d8ea8bf1083a42bf4f0bc92de22d9aae6291f474..119efa586e9d5a6df95fd6a9cbcf3c97d37e348a 100644
--- a/chrome/test/chromedriver/server/http_handler.cc
+++ b/chrome/test/chromedriver/server/http_handler.cc
@@ -61,6 +61,8 @@ CommandMapping::CommandMapping(HttpMethod method,
                                const Command& command)
     : method(method), path_pattern(path_pattern), command(command) {}
 
+CommandMapping::CommandMapping(const CommandMapping& other) = default;
+
 CommandMapping::~CommandMapping() {}
 
 HttpHandler::HttpHandler(const std::string& url_base)