Provide API in RequestCoordinator to remove results by client ID.

components/offline_pages/offline_page_item.cc

Index: components/offline_pages/offline_page_item.cc
diff --git a/components/offline_pages/offline_page_item.cc b/components/offline_pages/offline_page_item.cc
index 3fca9fcd47ee7076ce8aeb2d814b1c19f9c2af0c..55cf901766ccf80c5043cd6937be3e3469c70345 100644
--- a/components/offline_pages/offline_page_item.cc
+++ b/components/offline_pages/offline_page_item.cc
@@ -21,6 +21,13 @@ bool ClientId::operator==(const ClientId& client_id) const {
   return name_space == client_id.name_space && id == client_id.id;
 }
 
+bool ClientId::operator<(const ClientId& client_id) const {
+  if (name_space == client_id.name_space)
+    return (id < client_id.id);
+
+  return name_space < client_id.name_space;
+}
+
 OfflinePageItem::OfflinePageItem()
     : version(kCurrentVersion),
       file_size(0),