Add "has fast elements" bit to maps and use it in inlined keyed loads.

src/factory.cc

Index: src/factory.cc
diff --git a/src/factory.cc b/src/factory.cc
index 35d3c54e6646229f4c030679a3aa5e9f72c428bc..f6b93b0773cfa15f92ab88b21466ab0314e0ae99 100644
--- a/src/factory.cc
+++ b/src/factory.cc
@@ -274,11 +274,22 @@ Handle<Map> Factory::CopyMap(Handle<Map> src,
   return copy;
 }
 
+
 Handle<Map> Factory::CopyMapDropTransitions(Handle<Map> src) {
   CALL_HEAP_FUNCTION(src->CopyDropTransitions(), Map);
 }
 
 
+Handle<Map> Factory::GetFastElementsMap(Handle<Map> src) {
+  CALL_HEAP_FUNCTION(src->GetFastElementsMap(), Map);
+}
+
+
+Handle<Map> Factory::GetSlowElementsMap(Handle<Map> src) {
+  CALL_HEAP_FUNCTION(src->GetSlowElementsMap(), Map);
+}
+
+
 Handle<FixedArray> Factory::CopyFixedArray(Handle<FixedArray> array) {
   CALL_HEAP_FUNCTION(array->Copy(), FixedArray);
 }