Remove dead code from update_client::Component.

components/update_client/component.cc

 // Copyright 2017 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 "components/update_client/component.h"
 
 #include <algorithm>
 #include <utility>
 
 #include "base/bind.h"
@@ skipping 597 matching lines @@
 
   DCHECK_EQ(static_cast<int>(ErrorCategory::kErrorNone),
             component.error_category_);
   DCHECK_EQ(0, component.error_code_);
   DCHECK_EQ(0, component.extra_code1_);
 
   TransitionState(base::MakeUnique<StateUpdated>(&component));
 }
 
 Component::StateUpdating::StateUpdating(Component* component)
-    : State(component, ComponentState::kUpdating),
-      main_task_runner_(base::ThreadTaskRunnerHandle::Get()) {}
+    : State(component, ComponentState::kUpdating) {}
 
 Component::StateUpdating::~StateUpdating() {
   DCHECK(thread_checker_.CalledOnValidThread());
 }
 
 void Component::StateUpdating::DoHandle() {
   DCHECK(thread_checker_.CalledOnValidThread());
 
   const auto& component = Component::State::component();
   const auto& update_context = component.update_context_;
@@ skipping 64 matching lines @@
 Component::StateUninstalled::~StateUninstalled() {
   DCHECK(thread_checker_.CalledOnValidThread());
 }
 
 void Component::StateUninstalled::DoHandle() {
   DCHECK(thread_checker_.CalledOnValidThread());
   TransitionState(nullptr);
 }
 
 }  // namespace update_client