Fixing std::swap(x, x) in base.

base/pickle_unittest.cc

 // Copyright (c) 2012 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/pickle.h"
 
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 
@@ skipping 647 matching lines @@
   }
   {
     TestingPickle pickle;
     base::PickleSizer sizer;
     pickle.WriteBytes(testdata, testdatalen);
     sizer.AddBytes(testdatalen);
     EXPECT_EQ(sizer.payload_size(), pickle.payload_size());
   }
 }
 
+TEST(PickleTest, SelfSwap) {
+  TestingPickle pickle;
+  std::swap(pickle, pickle);
+}
+
 }  // namespace base