[gn] Enable stricter build flags

test/cctest/test-strings.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 1096 matching lines @@
 TEST(CachedHashOverflow) {
   CcTest::InitializeVM();
   // We incorrectly allowed strings to be tagged as array indices even if their
   // values didn't fit in the hash field.
   // See http://code.google.com/p/v8/issues/detail?id=728
   Isolate* isolate = CcTest::i_isolate();
 
   v8::HandleScope handle_scope(CcTest::isolate());
   // Lines must be executed sequentially. Combining them into one script
   // makes the bug go away.
-  const char* lines[] = {
-      "var x = [];",
-      "x[4] = 42;",
-      "var s = \"1073741828\";",
-      "x[s];",
-      "x[s] = 37;",
-      "x[4];",
-      "x[s];",
-      NULL
-  };
+  const char* lines[] = {"var x = [];", "x[4] = 42;", "var s = \"1073741828\";",
+                         "x[s];",       "x[s] = 37;", "x[4];",
+                         "x[s];"};
 
   Handle<Smi> fortytwo(Smi::FromInt(42), isolate);
   Handle<Smi> thirtyseven(Smi::FromInt(37), isolate);
   Handle<Object> results[] = { isolate->factory()->undefined_value(),
                                fortytwo,
                                isolate->factory()->undefined_value(),
                                isolate->factory()->undefined_value(),
                                thirtyseven,
                                fortytwo,
                                thirtyseven  // Bug yielded 42 here.
   };
 
-  const char* line;
   v8::Local<v8::Context> context = CcTest::isolate()->GetCurrentContext();
-  for (int i = 0; (line = lines[i]); i++) {
+  for (size_t i = 0; i < arraysize(lines); i++) {
+    const char* line = lines[i];
     printf("%s\n", line);
     v8::Local<v8::Value> result =
         v8::Script::Compile(context,
                             v8::String::NewFromUtf8(CcTest::isolate(), line,
                                                     v8::NewStringType::kNormal)
                                 .ToLocalChecked())
             .ToLocalChecked()
             ->Run(context)
             .ToLocalChecked();
     CHECK_EQ(results[i]->IsUndefined(CcTest::i_isolate()),
@@ skipping 512 matching lines @@
   CHECK_EQ(1, CompileRun("external.indexOf('', 1)")
                   ->Int32Value(context.local())
                   .FromJust());
   CHECK_EQ(-1, CompileRun("external.indexOf('a', 1)")
                    ->Int32Value(context.local())
                    .FromJust());
   CHECK_EQ(-1, CompileRun("external.indexOf('$')")
                    ->Int32Value(context.local())
                    .FromJust());
 }