[contexts] Place the initial JSArray maps on the native context directly.

src/crankshaft/hydrogen.cc

Index: src/crankshaft/hydrogen.cc
diff --git a/src/crankshaft/hydrogen.cc b/src/crankshaft/hydrogen.cc
index 98ec18dbe48ac5ef2b3138efc8fad3553f983414..08e6d1adb15da6f0de49e0025072d7e16408ee14 100644
--- a/src/crankshaft/hydrogen.cc
+++ b/src/crankshaft/hydrogen.cc
@@ -3427,16 +3427,9 @@ HValue* HGraphBuilder::JSArrayBuilder::EmitMapCode() {
       ? builder()->BuildGetNativeContext(constructor_function_)
       : builder()->BuildGetNativeContext();
 
-  HInstruction* index = builder()->Add<HConstant>(
-      static_cast<int32_t>(Context::JS_ARRAY_MAPS_INDEX));
-
-  HInstruction* map_array = builder()->Add<HLoadKeyed>(
-      native_context, index, nullptr, nullptr, FAST_ELEMENTS);
-
-  HInstruction* kind_index = builder()->Add<HConstant>(kind_);
-
-  return builder()->Add<HLoadKeyed>(map_array, kind_index, nullptr, nullptr,
-                                    FAST_ELEMENTS);
+  HObjectAccess access =
+      HObjectAccess::ForContextSlot(Context::ArrayMapIndex(kind_));
+  return builder()->Add<HLoadNamedField>(native_context, nullptr, access);
 }