[debug,api] Do not use embedder field for debug context id.

src/api.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/api.h"
 
 #include <string.h>  // For memcpy, strlen.
 #ifdef V8_USE_ADDRESS_SANITIZER
 #include <sanitizer/asan_interface.h>
 #endif  // V8_USE_ADDRESS_SANITIZER
@@ skipping 9027 matching lines @@
 void Debug::SetTailCallEliminationEnabled(Isolate* isolate, bool enabled) {
   i::Isolate* internal_isolate = reinterpret_cast<i::Isolate*>(isolate);
   internal_isolate->SetTailCallEliminationEnabled(enabled);
 }
 
 MaybeLocal<Array> Debug::GetInternalProperties(Isolate* v8_isolate,
                                                Local<Value> value) {
   return debug::GetInternalProperties(v8_isolate, value);
 }
 
+void debug::SetContextId(Local<Context> context, int id) {
+  Utils::OpenHandle(*context)->set_debug_context_id(i::Smi::FromInt(id));
+}
+
+int debug::GetContextId(Local<Context> context) {
+  i::Object* value = Utils::OpenHandle(*context)->debug_context_id();
+  return (value->IsSmi()) ? i::Smi::cast(value)->value() : 0;
+}
+
 Local<Context> debug::GetDebugContext(Isolate* isolate) {
   i::Isolate* i_isolate = reinterpret_cast<i::Isolate*>(isolate);
   ENTER_V8(i_isolate);
   return Utils::ToLocal(i_isolate->debug()->GetDebugContext());
 }
 
 MaybeLocal<Value> debug::Call(Local<Context> context,
                               v8::Local<v8::Function> fun,
                               v8::Local<v8::Value> data) {
   PREPARE_FOR_EXECUTION(context, Debug, Call, Value);
@@ skipping 1258 matching lines @@
   Address callback_address =
       reinterpret_cast<Address>(reinterpret_cast<intptr_t>(callback));
   VMState<EXTERNAL> state(isolate);
   ExternalCallbackScope call_scope(isolate, callback_address);
   callback(info);
 }
 
 
 }  // namespace internal
 }  // namespace v8