[debugger] do not enable liveedit by default.

src/debug/debug.cc

 // Copyright 2012 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 "src/debug/debug.h"
 
 #include <memory>
 
 #include "src/api.h"
 #include "src/arguments.h"
@@ skipping 24 matching lines @@
 #include "include/v8-debug.h"
 
 namespace v8 {
 namespace internal {
 
 Debug::Debug(Isolate* isolate)
     : debug_context_(Handle<Context>()),
       is_active_(false),
       hook_on_function_call_(false),
       is_suppressed_(false),
-      live_edit_enabled_(true),  // TODO(yangguo): set to false by default.
+      live_edit_enabled_(false),
       break_disabled_(false),
       break_points_active_(true),
       break_on_exception_(false),
       break_on_uncaught_exception_(false),
       side_effect_check_failed_(false),
       debug_info_list_(NULL),
       feature_tracker_(isolate),
       isolate_(isolate) {
   ThreadInit();
 }
@@ skipping 2396 matching lines @@
     isolate_->Throw(*isolate_->factory()->NewEvalError(
         MessageTemplate::kNoSideEffectDebugEvaluate));
   }
   isolate_->set_needs_side_effect_check(old_needs_side_effect_check_);
   isolate_->debug()->UpdateHookOnFunctionCall();
   isolate_->debug()->side_effect_check_failed_ = false;
 }
 
 }  // namespace internal
 }  // namespace v8