[debugger] whitelist some builtins as side-effect free.

src/debug/debug.h

 // 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.
 
 #ifndef V8_DEBUG_DEBUG_H_
 #define V8_DEBUG_DEBUG_H_
 
 #include "src/allocation.h"
 #include "src/arguments.h"
 #include "src/assembler.h"
@@ skipping 562 matching lines @@
 
   void UpdateState();
   void UpdateHookOnFunctionCall();
   void Unload();
   void SetNextBreakId() {
     thread_local_.break_id_ = ++thread_local_.break_count_;
   }
 
   // Check whether there are commands in the command queue.
   inline bool has_commands() const { return !command_queue_.IsEmpty(); }
-  inline bool ignore_events() const { return is_suppressed_ || !is_active_; }
+  inline bool ignore_events() const {
+    return is_suppressed_ || !is_active_ || isolate_->needs_side_effect_check();
+  }
   inline bool break_disabled() const {
     return break_disabled_ || in_debug_event_listener_;
   }
 
   void clear_suspended_generator() {
     thread_local_.suspended_generator_ = Smi::kZero;
   }
 
   bool has_suspended_generator() const {
     return thread_local_.suspended_generator_ != Smi::kZero;
@@ skipping 275 matching lines @@
                                   Handle<Code> code);
   static bool DebugBreakSlotIsPatched(Address pc);
   static void ClearDebugBreakSlot(Isolate* isolate, Address pc);
 };
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_DEBUG_DEBUG_H_