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

test/cctest/test-heap.cc

Index: test/cctest/test-heap.cc
===================================================================
--- test/cctest/test-heap.cc	(revision 654)
+++ test/cctest/test-heap.cc	(working copy)
@@ -248,9 +248,10 @@
 
 static void VerifyStringAllocation(const char* string) {
   String* s = String::cast(Heap::AllocateStringFromUtf8(CStrVector(string)));
-  CHECK_EQ(static_cast<int>(strlen(string)), s->length());
-  for (int index = 0; index < s->length(); index++) {
-    CHECK_EQ(static_cast<uint16_t>(string[index]), s->Get(index));  }
+  StringShape shape(s);
+  CHECK_EQ(static_cast<int>(strlen(string)), s->length(shape));
+  for (int index = 0; index < s->length(shape); index++) {
+    CHECK_EQ(static_cast<uint16_t>(string[index]), s->Get(shape, index));  }
 }