[for-in] Further refactorings and unification around for-in.

src/crankshaft/hydrogen.cc

Index: src/crankshaft/hydrogen.cc
diff --git a/src/crankshaft/hydrogen.cc b/src/crankshaft/hydrogen.cc
index d2ba73c1da65549651b0544019a1ff7c2463824c..974621aa31e88ae7f0e2d3e2a00bb1ba7dcab912 100644
--- a/src/crankshaft/hydrogen.cc
+++ b/src/crankshaft/hydrogen.cc
@@ -5340,7 +5340,7 @@ void HOptimizedGraphBuilder::BuildForInBody(ForInStatement* stmt,
     Push(enum_length);
     Add<HSimulate>(stmt->PrepareId());
   } else {
-    Runtime::FunctionId function_id = Runtime::kGetPropertyNamesFast;
+    Runtime::FunctionId function_id = Runtime::kForInEnumerate;
     Add<HPushArguments>(enumerable);
     HCallRuntime* array =
         Add<HCallRuntime>(Runtime::FunctionForId(function_id), 1);