[runtime] Use "the hole" instead of smi 0 as sentinel for context extension.

src/compiler/ast-graph-builder.cc

Index: src/compiler/ast-graph-builder.cc
diff --git a/src/compiler/ast-graph-builder.cc b/src/compiler/ast-graph-builder.cc
index a6cbfddfe4dae09748db199793b0cee28939b230..403e22bc196a3d8e1b736c4b1662a54545446b35 100644
--- a/src/compiler/ast-graph-builder.cc
+++ b/src/compiler/ast-graph-builder.cc
@@ -3858,8 +3858,8 @@ Node* AstGraphBuilder::TryLoadDynamicVariable(
       Node* load = NewNode(
           javascript()->LoadContext(depth, Context::EXTENSION_INDEX, false),
           current_context());
-      Node* check =
-          NewNode(javascript()->CallRuntime(Runtime::kInlineIsSmi, 1), load);
+      Node* check = NewNode(javascript()->StrictEqual(), load,
+                            jsgraph()->TheHoleConstant());
       fast_block.BreakUnless(check, BranchHint::kTrue);
     }
 
@@ -3900,8 +3900,8 @@ Node* AstGraphBuilder::TryLoadDynamicVariable(
       Node* load = NewNode(
           javascript()->LoadContext(depth, Context::EXTENSION_INDEX, false),
           current_context());
-      Node* check =
-          NewNode(javascript()->CallRuntime(Runtime::kInlineIsSmi, 1), load);
+      Node* check = NewNode(javascript()->StrictEqual(), load,
+                            jsgraph()->TheHoleConstant());
       fast_block.BreakUnless(check, BranchHint::kTrue);
     }