Make buildbots green. StringShapes can change during GC when we

shortcut cons strings.
Review URL: http://codereview.chromium.org/9245

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@681 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/handles.cc

@@ -217,8 +217,7 @@ Handle<Object> LookupSingleCharacterStringFromCode(uint32_t index) {
 
 
 Handle<String> SubString(Handle<String> str, int start, int end) {
-  StringShape shape(*str);
-  CALL_HEAP_FUNCTION(str->Slice(shape, start, end), String);
+  CALL_HEAP_FUNCTION(str->Slice(StringShape(*str), start, end), String);
 }