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

test/inspector/inspector-impl.cc

 // Copyright 2016 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 "test/inspector/inspector-impl.h"
 
 #include "include/v8.h"
 
 #include "src/vector.h"
 
 namespace {
 
-const int kInspectorClientIndex = v8::Context::kDebugIdIndex + 1;
+const int kInspectorClientIndex = 0;
 
 class ChannelImpl final : public v8_inspector::V8Inspector::Channel {
  public:
   explicit ChannelImpl(InspectorClientImpl::FrontendChannel* frontend_channel)
       : frontend_channel_(frontend_channel) {}
   virtual ~ChannelImpl() = default;
 
  private:
   void sendResponse(
       int callId,
@@ skipping 317 matching lines @@
 }
 
 void SendMessageToBackendExtension::SendMessageToBackend(
     const v8::FunctionCallbackInfo<v8::Value>& args) {
   CHECK(backend_task_runner_);
   CHECK(args.Length() == 2 && args[0]->IsString() && args[1]->IsInt32());
   v8::Local<v8::String> message = args[0].As<v8::String>();
   backend_task_runner_->Append(new SendMessageToBackendTask(
       ToVector(message), args[1].As<v8::Int32>()->Value()));
 }