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

components/history/core/browser/url_row.cc

Index: components/history/core/browser/url_row.cc
diff --git a/components/history/core/browser/url_row.cc b/components/history/core/browser/url_row.cc
index 71c37258cb4957326f1f09d3d249ad136ad0778c..096672d5180f78d4a75e91607db9b47e846336f1 100644
--- a/components/history/core/browser/url_row.cc
+++ b/components/history/core/browser/url_row.cc
@@ -24,6 +24,8 @@ URLRow::URLRow(const GURL& url, URLID id) : url_(url) {
   id_ = id;
 }
 
+URLRow::URLRow(const URLRow& other) = default;
+
 URLRow::~URLRow() {
 }
 
@@ -79,6 +81,8 @@ URLResult::URLResult(const URLRow& url_row)
       blocked_visit_(false) {
 }
 
+URLResult::URLResult(const URLResult& other) = default;
+
 URLResult::~URLResult() {
 }