api: introduce SealHandleScope

src/handles-inl.h

 // Copyright 2006-2008 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_HANDLES_INL_H_
 #define V8_HANDLES_INL_H_
 
 #include "src/api.h"
 #include "src/handles.h"
@@ skipping 120 matching lines @@
   prev_limit_ = current->limit;
   current->level++;
   return result;
 }
 
 
 template <typename T>
 T** HandleScope::CreateHandle(Isolate* isolate, T* value) {
   DCHECK(AllowHandleAllocation::IsAllowed());
   HandleScopeData* current = isolate->handle_scope_data();
+  DCHECK(current->level > 0);
 
   internal::Object** cur = current->next;
   if (cur == current->limit) cur = Extend(isolate);
   // Update the current next field, set the value in the created
   // handle, and return the result.
   DCHECK(cur < current->limit);
   current->next = cur + 1;
 
   T** result = reinterpret_cast<T**>(cur);
   *result = value;
@@ skipping 23 matching lines @@
   current->level = level_;
   DCHECK_EQ(current->next, current->limit);
   current->limit = limit_;
 }
 
 #endif
 
 } }  // namespace v8::internal
 
 #endif  // V8_HANDLES_INL_H_