Remove V8PerIsolateData::EnsureLiveRoot.

third_party/WebKit/Source/platform/bindings/V8PerIsolateData.cpp

 /*
  * Copyright (C) 2009 Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions
  * are met:
  * 1. Redistributions of source code must retain the above copyright
  *    notice, this list of conditions and the following disclaimer.
  * 2. Redistributions in binary form must reproduce the above copyright
  *    notice, this list of conditions and the following disclaimer in the
@@ skipping 73 matching lines @@
   isolate->SetData(gin::kEmbedderBlink, data);
   return isolate;
 }
 
 void V8PerIsolateData::EnableIdleTasks(
     v8::Isolate* isolate,
     std::unique_ptr<gin::V8IdleTaskRunner> task_runner) {
   From(isolate)->isolate_holder_.EnableIdleTasks(std::move(task_runner));
 }
 
-v8::Persistent<v8::Value>& V8PerIsolateData::EnsureLiveRoot() {
-  if (live_root_.IsEmpty())
-    live_root_.Set(GetIsolate(), v8::Null(GetIsolate()));
-  return live_root_.Get();
-}
-
 // willBeDestroyed() clear things that should be cleared before
 // ThreadState::detach() gets called.
 void V8PerIsolateData::WillBeDestroyed(v8::Isolate* isolate) {
   V8PerIsolateData* data = From(isolate);
 
   data->thread_debugger_.reset();
   // Clear any data that may have handles into the heap,
   // prior to calling ThreadState::detach().
   data->ClearEndOfScopeTasks();
 
   data->active_script_wrappables_.Clear();
 }
 
 // destroy() clear things that should be cleared after ThreadState::detach()
 // gets called but before the Isolate exits.
 void V8PerIsolateData::Destroy(v8::Isolate* isolate) {
   isolate->RemoveBeforeCallEnteredCallback(&BeforeCallEnteredCallback);
   isolate->RemoveMicrotasksCompletedCallback(&MicrotasksCompletedCallback);
   V8PerIsolateData* data = From(isolate);
 
   // Clear everything before exiting the Isolate.
   if (data->script_regexp_script_state_)
     data->script_regexp_script_state_->DisposePerContextData();
-  data->live_root_.Clear();
   data->private_property_.reset();
   data->string_cache_->Dispose();
   data->string_cache_.reset();
   data->interface_template_map_for_non_main_world_.clear();
   data->interface_template_map_for_main_world_.clear();
   data->operation_template_map_for_non_main_world_.clear();
   data->operation_template_map_for_main_world_.clear();
   if (IsMainThread())
     g_main_thread_per_isolate_data = 0;
 
@@ skipping 175 matching lines @@
   ScriptWrappableVisitor* current = CurrentVisitor();
   if (current)
     current->PerformCleanup();
 
   V8PerIsolateData::From(isolate_)->script_wrappable_visitor_.swap(
       saved_visitor_);
   isolate_->SetEmbedderHeapTracer(CurrentVisitor());
 }
 
 }  // namespace blink