Update from https://crrev.com/320931

base/ios/weak_nsobject_unittest.mm

 // Copyright 2013 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 "base/basictypes.h"
 #include "base/bind.h"
 #include "base/ios/weak_nsobject.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/message_loop/message_loop.h"
 #include "base/single_thread_task_runner.h"
@@ skipping 91 matching lines @@
 void TouchWeakData(const WeakNSObject<NSMutableData>& weak_data) {
   if (!weak_data)
     return;
   [weak_data increaseLengthBy:1];
 }
 
 // Makes a copy of |weak_object| on the current thread and posts a task to touch
 // the weak object on its original thread.
 void CopyWeakNSObjectAndPost(const WeakNSObject<NSMutableData>& weak_object,
                              scoped_refptr<SingleThreadTaskRunner> runner) {
-  WeakNSObject<NSMutableData> weak_copy(weak_object);
-  runner->PostTask(FROM_HERE, Bind(&TouchWeakData, weak_copy));
+  // Copy using constructor.
+  WeakNSObject<NSMutableData> weak_copy1(weak_object);
+  runner->PostTask(FROM_HERE, Bind(&TouchWeakData, weak_copy1));
+  // Copy using assignment operator.
+  WeakNSObject<NSMutableData> weak_copy2 = weak_object;
+  runner->PostTask(FROM_HERE, Bind(&TouchWeakData, weak_copy2));
 }
 
 // Tests that the weak object can be copied on a different thread.
 TEST(WeakNSObjectTest, WeakNSObjectCopyOnOtherThread) {
   MessageLoop loop;
   Thread other_thread("WeakNSObjectCopyOnOtherThread");
   other_thread.Start();
 
   scoped_nsobject<NSMutableData> data([[NSMutableData alloc] init]);
   WeakNSObject<NSMutableData> weak(data);
 
   scoped_refptr<SingleThreadTaskRunner> runner = loop.task_runner();
   other_thread.task_runner()->PostTask(
       FROM_HERE, Bind(&CopyWeakNSObjectAndPost, weak, runner));
   other_thread.Stop();
   loop.RunUntilIdle();
 
-  // Check that TouchWeakData was called.
-  EXPECT_EQ(1u, [data length]);
+  // Check that TouchWeakData was called and the object touched twice.
+  EXPECT_EQ(2u, [data length]);
 }
 
 }  // namespace
 }  // namespace base