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

components/bookmarks/browser/bookmark_node_data.cc

Index: components/bookmarks/browser/bookmark_node_data.cc
diff --git a/components/bookmarks/browser/bookmark_node_data.cc b/components/bookmarks/browser/bookmark_node_data.cc
index 83d160f39fcef71ddba38b38035ee02d25961ccd..e634fd3c7b86f200f60a7e363a17ff0fee7e5d19 100644
--- a/components/bookmarks/browser/bookmark_node_data.cc
+++ b/components/bookmarks/browser/bookmark_node_data.cc
@@ -34,6 +34,8 @@ BookmarkNodeData::Element::Element(const BookmarkNode* node)
     children.push_back(Element(node->GetChild(i)));
 }
 
+BookmarkNodeData::Element::Element(const Element& other) = default;
+
 BookmarkNodeData::Element::~Element() {
 }
 
@@ -101,6 +103,8 @@ bool BookmarkNodeData::Element::ReadFromPickle(base::PickleIterator* iterator) {
 BookmarkNodeData::BookmarkNodeData() {
 }
 
+BookmarkNodeData::BookmarkNodeData(const BookmarkNodeData& other) = default;
+
 BookmarkNodeData::BookmarkNodeData(const BookmarkNode* node) {
   elements.push_back(Element(node));
 }