Removed some unsafe uses of StringShape....

src/objects.h

Index: src/objects.h
===================================================================
--- src/objects.h	(revision 694)
+++ src/objects.h	(working copy)
@@ -3024,7 +3024,9 @@
 // the shape of the string is given its own class so that it can be retrieved
 // once and used for several string operations.  A StringShape is small enough
 // to be passed by value and is immutable, but be aware that flattening a
-// string can potentially alter its shape.
+// string can potentially alter its shape.  Also be aware that a GC caused by
+// something else can alter the shape of a string due to ConsString
+// shortcutting.
 //
 // Most of the methods designed to interrogate a string as to its exact nature
 // have been made into methods on StringShape in order to encourage the use of
@@ -3116,7 +3118,7 @@
   bool MarkAsUndetectable();
 
   // Slice the string and return a substring.
-  Object* Slice(StringShape shape, int from, int to);
+  Object* Slice(int from, int to);
 
   // String equality operations.
   inline bool Equals(String* other);
@@ -3471,9 +3473,6 @@
   // Dispatched behavior.
   uint16_t SlicedStringGet(int index);
 
-  // Flatten any ConsString hiding behind this SlicedString.
-  Object* SlicedStringFlatten();
-
   // Casting.
   static inline SlicedString* cast(Object* obj);