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

tools/gn/parse_tree_unittest.cc

Index: tools/gn/parse_tree_unittest.cc
diff --git a/tools/gn/parse_tree_unittest.cc b/tools/gn/parse_tree_unittest.cc
index f5edbc8f064d7b9be8b680b2a069b125b23bbb9b..a6850a74850fe7184a2303366a6d98bcb537747c 100644
--- a/tools/gn/parse_tree_unittest.cc
+++ b/tools/gn/parse_tree_unittest.cc
@@ -225,7 +225,7 @@ TEST(ParseTree, Integers) {
       "9223372036854775807",   // INT64_MAX
       "-9223372036854775808",  // INT64_MIN
   };
-  for (auto s : kGood) {
+  for (auto* s : kGood) {
     TestParseInput input(std::string("x = ") + s);
     EXPECT_FALSE(input.has_error());
 
@@ -242,7 +242,7 @@ TEST(ParseTree, Integers) {
       "9223372036854775808",   // INT64_MAX + 1
       "-9223372036854775809",  // INT64_MIN - 1
   };
-  for (auto s : kBad) {
+  for (auto* s : kBad) {
     TestParseInput input(std::string("x = ") + s);
     EXPECT_FALSE(input.has_error());