src: use a higher limit in the NearHeapLimitCallback

V8 requires the NearHeapLimitCallback to return a limit that's higher
than the initial one or otherwise it will crash.

Author: joyeecheung

src/env.cc

@@ -1631,7 +1631,10 @@ size_t Environment::NearHeapLimitCallback(void* data,
   env->isolate()->AutomaticallyRestoreInitialHeapLimit(0.95);
 
   env->is_processing_heap_limit_callback_ = false;
-  return initial_heap_limit;
+
+  // The new limit must be higher than initial_heap_limit or V8 might
+  // crash.
+  return initial_heap_limit + 1;
 }
 
 inline size_t Environment::SelfSize() const {