Control ES2015 'Tail call elimination' language feature via finch flag.

gin/isolate_holder.cc

 // Copyright 2013 The Chromium 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 "gin/public/isolate_holder.h"
 
 #include <stddef.h>
 #include <stdlib.h>
 #include <string.h>
 #include <utility>
 
+#include "base/feature_list.h"
 #include "base/logging.h"
 #include "base/message_loop/message_loop.h"
 #include "base/sys_info.h"
 #include "gin/debug_impl.h"
 #include "gin/function_template.h"
 #include "gin/per_isolate_data.h"
 #include "gin/run_microtasks_observer.h"
 #include "gin/v8_initializer.h"
 #include "gin/v8_isolate_memory_dump_provider.h"
 
@@ skipping 52 matching lines @@
   isolate_ = NULL;
 }
 
 // static
 void IsolateHolder::Initialize(ScriptMode mode,
                                V8ExtrasMode v8_extras_mode,
                                v8::ArrayBuffer::Allocator* allocator) {
   CHECK(allocator);
   V8Initializer::Initialize(mode, v8_extras_mode);
   g_array_buffer_allocator = allocator;
+
+  // Initialize an instance of FeatureList. This will be a no-op if an instance
+  // was already set up by the embedder.
+  base::FeatureList::InitializeInstance();
+
+  const base::Feature kES2015TailCallsFeature {
+    "V8_ES2015_TailCalls", base::FEATURE_DISABLED_BY_DEFAULT
+  };
+  if (base::FeatureList::IsEnabled(kES2015TailCallsFeature)) {
+    static const char harmony_tailcalls[] = "--harmony-tailcalls";
+    v8::V8::SetFlagsFromString(harmony_tailcalls,
+                               sizeof(harmony_tailcalls) - 1);
+  }
 }
 
 void IsolateHolder::AddRunMicrotasksObserver() {
   DCHECK(!task_observer_.get());
   task_observer_.reset(new RunMicrotasksObserver(isolate_));
   base::MessageLoop::current()->AddTaskObserver(task_observer_.get());
 }
 
 void IsolateHolder::RemoveRunMicrotasksObserver() {
   DCHECK(task_observer_.get());
   base::MessageLoop::current()->RemoveTaskObserver(task_observer_.get());
   task_observer_.reset();
 }
 
 void IsolateHolder::EnableIdleTasks(
     scoped_ptr<V8IdleTaskRunner> idle_task_runner) {
   DCHECK(isolate_data_.get());
   isolate_data_->EnableIdleTasks(std::move(idle_task_runner));
 }
 
 }  // namespace gin