Enable compiling GN by default.

tools/gn/operators.cc

 // Copyright (c) 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 "tools/gn/operators.h"
 
 #include "base/strings/string_number_conversions.h"
 #include "tools/gn/err.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scope.h"
@@ skipping 109 matching lines @@
       // list item. This is to detect the case where you write
       //   defines = ["FOO"]
       // and you overwrote inherited ones, when instead you mean to append:
       //   defines += ["FOO"]
       if (old_value->type() == Value::LIST &&
           !old_value->list_value().empty() &&
           right.type() == Value::LIST &&
           !right.list_value().empty()) {
         *err = Err(op_node->left()->GetRange(), "Replacing nonempty list.",
             std::string("This overwrites a previously-defined nonempty list ") +
-            "(length " + base::IntToString(old_value->list_value().size()) +
-            ").");
+            "(length " +
+            base::IntToString(static_cast<int>(old_value->list_value().size()))
+            + ").");
         err->AppendSubErr(Err(*old_value, "for previous definition",
             "with another one (length " +
-            base::IntToString(right.list_value().size()) + "). Did you mean " +
+            base::IntToString(static_cast<int>(right.list_value().size())) +
+            "). Did you mean " +
             "\"+=\" to append instead? If you\nreally want to do this, do\n  " +
             left.value().as_string() + " = []\nbefore reassigning."));
         return Value();
       }
     }
   }
   if (err->has_error())
     return Value();
 
   if (right.type() == Value::LIST && left.value() == kSourcesName) {
@@ skipping 435 matching lines @@
     return ExecuteLess(scope, op_node, left_value, right_value, err);
 
   // ||, &&.
   if (op.type() == Token::BOOLEAN_OR)
     return ExecuteOr(scope, op_node, left_value, right_value, err);
   if (op.type() == Token::BOOLEAN_AND)
     return ExecuteAnd(scope, op_node, left_value, right_value, err);
 
   return Value();
 }