rewrite_to_chrome_style: Make const decisions aware of const variables

tools/clang/rewrite_to_chrome_style/tests/template-original.cc

 // Copyright 2016 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 <type_traits>
 
 namespace not_blink {
 
 void function(int x) {}
 
@@ skipping 45 matching lines @@
   const int maybeAConstToo = sizeof(T);
   const int isAConstToo = number;
   // These are built from calls to functions which produces inconsistent
   // results so they should not be considered const to be safe.
   const bool fromAMethod = functionNotMarkedConstexpr(number);
   const bool fromATemplatedMethod = templatedFunctionNotMarkedConstexpr(number);
   // A complex statement of const things is const.
   const bool complexConst = number || (number + 1);
   // A complex statement with a non-const thing is not const.
   const bool complexNotConst = number || (g_globalNumber + 1);
+  // A const built from other consts is a const.
+  const bool constFromAConst = complexConst || number;
 }
 
 template <int number, typename... T>
 void F() {
   // These are const but hacker_case so we leave them alone.
   const int maybe_a_const = sizeof...(T);
   const int is_a_const = number;
   // These are const expressions so they get a k prefix.
   const int maybeAConstToo = sizeof...(T);
   const int isAConstToo = number;
@@ skipping 292 matching lines @@
     // Need to rewrite |f| to |F| below (because this method name
     // does get rewritten when processing blink::test_unnamed_arg::Class).
     // See also https://crbug.com/670434.
     output->f(123);
   }
 };
 
 }  // namespace blink_methods_called_from_mojo_traits_are_not_rewritten
 
 }  // namespace not_blink