tools/gn: Change auto to not deduce raw pointers.

tools/gn/input_conversion_unittest.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 "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/err.h"
 #include "tools/gn/input_conversion.h"
 #include "tools/gn/input_file.h"
 #include "tools/gn/parse_tree.h"
 #include "tools/gn/scheduler.h"
@@ skipping 140 matching lines @@
       "print(5)",
 
       // Trailing junk not allowed.
       "233105-1",
 
       // Non-literals hidden in arrays are not allowed.
       "[233105 - 1]",
       "[rebase_path(\"//\")]",
   };
 
-  for (auto test : kTests) {
+  for (auto* test : kTests) {
     Err err;
     std::string input(test);
     Value result = ConvertInputToValue(settings(), input, nullptr,
                                        Value(nullptr, "value"), &err);
     EXPECT_TRUE(err.has_error()) << test;
   }
 }
 
 // Passing none or the empty string for input conversion should ignore the
 // result.
 TEST_F(InputConversionTest, Ignore) {
   Err err;
   Value result = ConvertInputToValue(settings(), "foo", nullptr, Value(), &err);
   EXPECT_FALSE(err.has_error());
   EXPECT_EQ(Value::NONE, result.type());
 
   result =
       ConvertInputToValue(settings(), "foo", nullptr, Value(nullptr, ""), &err);
   EXPECT_FALSE(err.has_error());
   EXPECT_EQ(Value::NONE, result.type());
 }