Do not reflect uninitialized 'let' and 'const' in scope mirrors.

src/scopeinfo.cc

 // Copyright 2011 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include <stdlib.h>
 
 #include "src/v8.h"
 
 #include "src/scopeinfo.h"
 #include "src/scopes.h"
@@ skipping 362 matching lines @@
                                                Handle<JSObject> scope_object) {
   Isolate* isolate = scope_info->GetIsolate();
   int local_count = scope_info->ContextLocalCount();
   if (local_count == 0) return true;
   // Fill all context locals to the context extension.
   int first_context_var = scope_info->StackLocalCount();
   int start = scope_info->ContextLocalNameEntriesIndex();
   for (int i = 0; i < local_count; ++i) {
     if (scope_info->LocalIsSynthetic(first_context_var + i)) continue;
     int context_index = Context::MIN_CONTEXT_SLOTS + i;
+    Handle<Object> value = Handle<Object>(context->get(context_index), isolate);
+    // Do not reflect variables under TDZ in scope object.
+    if (value->IsTheHole()) continue;
     RETURN_ON_EXCEPTION_VALUE(
-        isolate,
-        Runtime::DefineObjectProperty(
-            scope_object,
-            Handle<String>(String::cast(scope_info->get(i + start))),
-            Handle<Object>(context->get(context_index), isolate),
-            ::NONE),
+        isolate, Runtime::DefineObjectProperty(
+                     scope_object,
+                     Handle<String>(String::cast(scope_info->get(i + start))),
+                     value, ::NONE),
         false);
   }
   return true;
 }
 
 
 int ScopeInfo::ParameterEntriesIndex() {
   DCHECK(length() > 0);
   return kVariablePartIndex;
 }
@@ skipping 164 matching lines @@
     } else {
       DCHECK(var->index() >= 0);
       info->set_index(i, var->index());
     }
   }
   DCHECK(i == info->length());
   return info;
 }
 
 } }  // namespace v8::internal