reland of [sync] Add Sessions integration tests

components/sync/test/fake_server/sessions_hierarchy.cc

 // Copyright 2015 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "components/sync/test/fake_server/sessions_hierarchy.h"
 
 #include <sstream>
 
 namespace fake_server {
 
 SessionsHierarchy::SessionsHierarchy() {}
 
+SessionsHierarchy::SessionsHierarchy(const SessionsHierarchy& other) = default;
+
+SessionsHierarchy::SessionsHierarchy(
+    std::initializer_list<std::multiset<std::string>> windows)
+    : windows_(windows) {}
+
 SessionsHierarchy::~SessionsHierarchy() {}
 
 void SessionsHierarchy::AddWindow(const std::string& tab) {
-  SessionsHierarchy::Window window;
-  window.insert(tab);
-  windows_.insert(window);
+  windows_.insert({tab});
 }
 
 void SessionsHierarchy::AddWindow(const std::multiset<std::string>& tabs) {
   windows_.insert(tabs);
 }
 
 std::string SessionsHierarchy::ToString() const {
   std::stringstream output;
   output << "{";
   for (WindowContainer::const_iterator window_it = windows_.begin();
@@ skipping 13 matching lines @@
   }
   output << "}";
   return output.str();
 }
 
 bool SessionsHierarchy::Equals(const SessionsHierarchy& other) const {
   return windows_ == other.windows_;
 }
 
 }  // namespace fake_server