[Chromoting] Refactor the host policy watcher so that policies can easily be added.

remoting/host/policy_hack/nat_policy.cc

-// Copyright (c) 2012 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.
-
-// Most of this code is copied from:
-//   src/chrome/browser/policy/asynchronous_policy_loader.{h,cc}
-
-#include "remoting/host/policy_hack/nat_policy.h"
-
-#include "base/bind.h"
-#include "base/compiler_specific.h"
-#include "base/location.h"
-#include "base/memory/weak_ptr.h"
-#include "base/single_thread_task_runner.h"
-#include "base/synchronization/waitable_event.h"
-#include "base/time.h"
-#include "base/values.h"
-
-namespace remoting {
-namespace policy_hack {
-
-namespace {
-// The time interval for rechecking policy. This is our fallback in case the
-// delegate never reports a change to the ReloadObserver.
-const int kFallbackReloadDelayMinutes = 15;
-
-}  // namespace
-
-const char NatPolicy::kNatPolicyName[] = "RemoteAccessHostFirewallTraversal";
-
-NatPolicy::NatPolicy(scoped_refptr<base::SingleThreadTaskRunner> task_runner)
-    : task_runner_(task_runner),
-      current_nat_enabled_state_(false),
-      first_state_published_(false),
-      ALLOW_THIS_IN_INITIALIZER_LIST(weak_factory_(this)) {
-}
-
-NatPolicy::~NatPolicy() {
-}
-
-void NatPolicy::StartWatching(const NatEnabledCallback& nat_enabled_cb) {
-  if (!OnPolicyThread()) {
-    task_runner_->PostTask(FROM_HERE,
-                           base::Bind(&NatPolicy::StartWatching,
-                                      base::Unretained(this),
-                                      nat_enabled_cb));
-    return;
-  }
-
-  nat_enabled_cb_ = nat_enabled_cb;
-  StartWatchingInternal();
-}
-
-void NatPolicy::StopWatching(base::WaitableEvent* done) {
-  if (!OnPolicyThread()) {
-    task_runner_->PostTask(FROM_HERE,
-                           base::Bind(&NatPolicy::StopWatching,
-                                      base::Unretained(this), done));
-    return;
-  }
-
-  StopWatchingInternal();
-  weak_factory_.InvalidateWeakPtrs();
-  nat_enabled_cb_.Reset();
-
-  done->Signal();
-}
-
-void NatPolicy::ScheduleFallbackReloadTask() {
-  DCHECK(OnPolicyThread());
-  ScheduleReloadTask(
-      base::TimeDelta::FromMinutes(kFallbackReloadDelayMinutes));
-}
-
-void NatPolicy::ScheduleReloadTask(const base::TimeDelta& delay) {
-  DCHECK(OnPolicyThread());
-  task_runner_->PostDelayedTask(
-      FROM_HERE,
-      base::Bind(&NatPolicy::Reload, weak_factory_.GetWeakPtr()),
-      delay);
-}
-
-bool NatPolicy::OnPolicyThread() const {
-  return task_runner_->BelongsToCurrentThread();
-}
-
-void NatPolicy::UpdateNatPolicy(base::DictionaryValue* new_policy) {
-  DCHECK(OnPolicyThread());
-  bool new_nat_enabled_state = false;
-  if (!new_policy->HasKey(kNatPolicyName)) {
-    // If unspecified, the default value of this policy is true.
-    new_nat_enabled_state = true;
-  } else {
-    // Otherwise, try to parse the value and only change from false if we get
-    // a successful read.
-    base::Value* value;
-    if (new_policy->Get(kNatPolicyName, &value) &&
-        value->IsType(base::Value::TYPE_BOOLEAN)) {
-      CHECK(value->GetAsBoolean(&new_nat_enabled_state));
-    }
-  }
-
-  if (!first_state_published_ ||
-      (new_nat_enabled_state != current_nat_enabled_state_)) {
-    first_state_published_ = true;
-    current_nat_enabled_state_ = new_nat_enabled_state;
-    nat_enabled_cb_.Run(current_nat_enabled_state_);
-  }
-}
-
-}  // namespace policy_hack
-}  // namespace remoting