Put ThinStrings behind a flag (off by default)

test/cctest/test-code-stub-assembler.cc

Index: test/cctest/test-code-stub-assembler.cc
diff --git a/test/cctest/test-code-stub-assembler.cc b/test/cctest/test-code-stub-assembler.cc
index 072ae4dff5be832ff4b4fe85a45ab4b5fc5a7578..b179e27edcd196ddc8e6e19bb1bece24222a5c57 100644
--- a/test/cctest/test-code-stub-assembler.cc
+++ b/test/cctest/test-code-stub-assembler.cc
@@ -313,14 +313,14 @@ TEST(TryToName) {
     ft.CheckTrue(key, expect_bailout);
   }
 
-  {
+  if (FLAG_thin_strings) {
     // TryToName(<thin string>) => internalized version.
     Handle<String> s = isolate->factory()->NewStringFromAsciiChecked("foo");
     Handle<String> internalized = isolate->factory()->InternalizeString(s);
     ft.CheckTrue(s, expect_unique, internalized);
   }
 
-  {
+  if (FLAG_thin_strings) {
     // TryToName(<thin two-byte string>) => internalized version.
     uc16 array1[] = {2001, 2002, 2003};
     Vector<const uc16> str1(array1);