Removed some unsafe uses of StringShape....

src/conversions.cc

Index: src/conversions.cc
===================================================================
--- src/conversions.cc	(revision 694)
+++ src/conversions.cc	(working copy)
@@ -121,15 +121,14 @@
 
 
 static inline bool SubStringEquals(String* str, int index, const char* other) {
-  StringShape shape(str);
   HandleScope scope;
-  int str_length = str->length(shape);
+  int str_length = str->length();
   int other_length = strlen(other);
   int end = index + other_length < str_length ?
             index + other_length :
             str_length;
   Handle<String> slice =
-      Factory::NewStringSlice(Handle<String>(str), shape, index, end);
+      Factory::NewStringSlice(Handle<String>(str), index, end);
   return slice->IsEqualTo(Vector<const char>(other, other_length));
 }