Avoid HeapObject check in HStoreNamedField.

src/arm/lithium-arm.cc

Index: src/arm/lithium-arm.cc
diff --git a/src/arm/lithium-arm.cc b/src/arm/lithium-arm.cc
index 5e4b23efd2be169ccf4f8af65ff70885f65c8a29..f494df8c0593d50f9e2280468aaa9ff82cb18ef6 100644
--- a/src/arm/lithium-arm.cc
+++ b/src/arm/lithium-arm.cc
@@ -2316,13 +2316,7 @@ LInstruction* LChunkBuilder::DoStoreNamedField(HStoreNamedField* instr) {
   // We need a temporary register for write barrier of the map field.
   LOperand* temp = needs_write_barrier_for_map ? TempRegister() : NULL;
 
-  LInstruction* result = new(zone()) LStoreNamedField(obj, val, temp);
-  if (!instr->access().IsExternalMemory() &&
-      instr->field_representation().IsHeapObject() &&
-      !instr->value()->type().IsHeapObject()) {
-    result = AssignEnvironment(result);
-  }
-  return result;
+  return new(zone()) LStoreNamedField(obj, val, temp);
 }