[Interpreter] Avoid accessing Isolate from during bytecode generation.

src/ast/scopes.h

Index: src/ast/scopes.h
diff --git a/src/ast/scopes.h b/src/ast/scopes.h
index dd65d48c4a14c4e234e958c8ddc8c1a78648fdf0..f412ec2dbc751bb5c555154742379846d298403c 100644
--- a/src/ast/scopes.h
+++ b/src/ast/scopes.h
@@ -412,8 +412,15 @@ class Scope: public ZoneObject {
   // 'this' is bound, and what determines the function kind.
   DeclarationScope* GetReceiverScope();
 
+  // Creates a scope info if it doesn't already exist.
   Handle<ScopeInfo> GetScopeInfo(Isolate* isolate);
 
+  // GetScopeInfo() must have been called once to create the ScopeInfo.
+  Handle<ScopeInfo> scope_info() {
+    DCHECK(!scope_info_.is_null());
+    return scope_info_;
+  }
+
   // ---------------------------------------------------------------------------
   // Strict mode support.
   bool IsDeclared(const AstRawString* name) {