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

base/values.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/values.h"
 
 #include <string.h>
 
 #include <algorithm>
 #include <cmath>
@@ skipping 167 matching lines @@
   } else {
     // This is not a self assignment because the type_ doesn't match.
     InternalCleanup();
     InternalCopyConstructFrom(that);
   }
 
   return *this;
 }
 
 Value& Value::operator=(Value&& that) noexcept {
-  DCHECK(this != &that) << "attempt to self move assign.";
   InternalCleanup();
   InternalMoveConstructFrom(std::move(that));
 
   return *this;
 }
 
 Value::~Value() {
   InternalCleanup();
 }
 
@@ skipping 1144 matching lines @@
 }
 
 std::ostream& operator<<(std::ostream& out, const Value::Type& type) {
   if (static_cast<int>(type) < 0 ||
       static_cast<size_t>(type) >= arraysize(kTypeNames))
     return out << "Invalid Type (index = " << static_cast<int>(type) << ")";
   return out << Value::GetTypeName(type);
 }
 
 }  // namespace base