Reduce the memory usage of bookmarks storage

components/bookmarks/browser/bookmark_node.h

Index: components/bookmarks/browser/bookmark_node.h
diff --git a/components/bookmarks/browser/bookmark_node.h b/components/bookmarks/browser/bookmark_node.h
index d125c44e52c92806cea31a7297925411baba0182..c3d26e50e15e2eddb87aabc2b22f66e8c116e60a 100644
--- a/components/bookmarks/browser/bookmark_node.h
+++ b/components/bookmarks/browser/bookmark_node.h
@@ -10,6 +10,7 @@
 #include <memory>
 
 #include "base/macros.h"
+#include "base/memory/ptr_util.h"
 #include "base/task/cancelable_task_tracker.h"
 #include "base/time/time.h"
 #include "components/bookmarks/browser/titled_url_node.h"
@@ -69,7 +70,7 @@ class BookmarkNode : public ui::TreeNode<BookmarkNode>, public TitledUrlNode {
 
   // Returns the favicon's URL. Returns an empty URL if there is no favicon
   // associated with this bookmark.
-  const GURL& icon_url() const { return icon_url_; }
+  const GURL* icon_url() const { return icon_url_ ? icon_url_.get() : nullptr; }
 
   Type type() const { return type_; }
   void set_type(Type type) { type_ = type; }
@@ -134,7 +135,7 @@ class BookmarkNode : public ui::TreeNode<BookmarkNode>, public TitledUrlNode {
 
   // Sets the favicon's URL.
   void set_icon_url(const GURL& icon_url) {
-    icon_url_ = icon_url;
+    icon_url_ = base::MakeUnique<GURL>(icon_url);
   }
 
   // Returns the favicon. In nearly all cases you should use the method
@@ -179,7 +180,7 @@ class BookmarkNode : public ui::TreeNode<BookmarkNode>, public TitledUrlNode {
   favicon_base::IconType favicon_type_;
 
   // The URL of the node's favicon.
-  GURL icon_url_;
+  std::unique_ptr<GURL> icon_url_;
 
   // The loading state of the favicon.
   FaviconState favicon_state_;