[Interpreter] Add support for Load / Store to Lookup slots.

src/interpreter/bytecode-generator.cc

Index: src/interpreter/bytecode-generator.cc
diff --git a/src/interpreter/bytecode-generator.cc b/src/interpreter/bytecode-generator.cc
index 486d432126c9300b07f6980d10dd96b999b5e557..ff5913ace9963ff70269a4ea7272341854772f41 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -1344,8 +1344,12 @@ void BytecodeGenerator::VisitVariableLoad(Variable* variable,
       // let variables.
       break;
     }
-    case VariableLocation::LOOKUP:
-      UNIMPLEMENTED();
+    case VariableLocation::LOOKUP: {
+      builder()->LoadLookupSlot(variable->name(), execution_context()->reg(),
+                                typeof_mode);
+      execution_result()->SetResultInAccumulator();
+      break;
+    }
   }
 }
 
@@ -1421,8 +1425,11 @@ void BytecodeGenerator::VisitVariableAssignment(Variable* variable,
       builder()->StoreContextSlot(context_reg, variable->index());
       break;
     }
-    case VariableLocation::LOOKUP:
-      UNIMPLEMENTED();
+    case VariableLocation::LOOKUP: {
+      builder()->StoreLookupSlot(variable->name(), execution_context()->reg(),
+                                 language_mode());
+      break;
+    }
   }
 }