Create an abstraction for the string type flags so that they can be cached....

src/prettyprinter.cc

Index: src/prettyprinter.cc
===================================================================
--- src/prettyprinter.cc	(revision 654)
+++ src/prettyprinter.cc	(working copy)
@@ -503,9 +503,10 @@
   Object* object = *value;
   if (object->IsString()) {
     String* string = String::cast(object);
+    StringShape shape(string);
     if (quote) Print("\"");
-    for (int i = 0; i < string->length(); i++) {
-      Print("%c", string->Get(i));
+    for (int i = 0; i < string->length(shape); i++) {
+      Print("%c", string->Get(shape, i));
     }
     if (quote) Print("\"");
   } else if (object == Heap::null_value()) {