Reland "Migrate PrivetTrafficDetector to use NetworkConnectionTracker."

This is a reland of 9b785217 with test
fixes. The failing unit tests weren't being run when I first landed
this, but were enabled afterwards and started breaking, so I rolled
back.

Specifically, I PostTask'd (un)registering with the
NetworkConnectionTracker to the right threads, and added a
PrivetTrafficDetector::Stop method to clean up the registration and
call it from PrivetNotificationService.

Original change's description:
> Migrate PrivetTrafficDetector to use NetworkConnectionTracker.
>
> This migrates PrivetTrafficDetector from using
> net::NetworkChangeNotifier to content::NetworkConnectionTracker, which
> works with the network service enabled.
>
> Bug: 859134
> Change-Id: I06f2ecbe142bbed9a8772f69ab109b0c0dc32581
> Reviewed-on: https://chromium-review.googlesource.com/1123681
> Reviewed-by: Julian Pastarmov <pastarmovj@chromium.org>
> Reviewed-by: Lei Zhang <thestig@chromium.org>
> Commit-Queue: Robbie McElrath <rmcelrath@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#574700}

Bug: 859134
Change-Id: I19bc5bf0abdbd41cfbd3da1c0881f122adca6c2b
Reviewed-on: https://chromium-review.googlesource.com/1137411Reviewed-by: Lei Zhang <thestig@chromium.org>
Reviewed-by: Helen Li <xunjieli@chromium.org>
Commit-Queue: Robbie McElrath <rmcelrath@chromium.org>
Cr-Commit-Position: refs/heads/master@{#576278}

chrome/browser/printing/cloud_print/privet_notifications.cc

@@ -209,6 +209,11 @@ PrivetNotificationService::PrivetNotificationService(
 }
 
 PrivetNotificationService::~PrivetNotificationService() {
+#if BUILDFLAG(ENABLE_MDNS)
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  if (traffic_detector_)
+    traffic_detector_->Stop();
+#endif
 }
 
 void PrivetNotificationService::DeviceChanged(

chrome/browser/printing/cloud_print/privet_traffic_detector.cc

@@ -14,8 +14,10 @@
 #include "base/task_scheduler/post_task.h"
 #include "base/threading/thread_restrictions.h"
 #include "base/threading/thread_task_runner_handle.h"
+#include "chrome/browser/browser_process.h"
 #include "net/base/ip_address.h"
 #include "net/base/net_errors.h"
+#include "net/base/network_change_notifier.h"
 #include "net/base/network_interfaces.h"
 #include "net/dns/dns_protocol.h"
 #include "net/dns/dns_response.h"
@@ -74,30 +76,42 @@ PrivetTrafficDetector::PrivetTrafficDetector(
       restart_attempts_(kMaxRestartAttempts),
       weak_ptr_factory_(this) {}
 
+PrivetTrafficDetector::~PrivetTrafficDetector() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
+}
+
 void PrivetTrafficDetector::Start() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  g_browser_process->network_connection_tracker()->AddNetworkConnectionObserver(
+      this);
   content::BrowserThread::PostTask(
       content::BrowserThread::IO, FROM_HERE,
-      base::BindOnce(&PrivetTrafficDetector::StartOnIOThread,
+      base::BindOnce(&PrivetTrafficDetector::ScheduleRestart,
                      weak_ptr_factory_.GetWeakPtr()));
 }
 
-PrivetTrafficDetector::~PrivetTrafficDetector() {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
-  net::NetworkChangeNotifier::RemoveNetworkChangeObserver(this);
+void PrivetTrafficDetector::Stop() {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  g_browser_process->network_connection_tracker()
+      ->RemoveNetworkConnectionObserver(this);
 }
 
-void PrivetTrafficDetector::StartOnIOThread() {
-  DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
-  net::NetworkChangeNotifier::AddNetworkChangeObserver(this);
-  ScheduleRestart();
+void PrivetTrafficDetector::OnConnectionChanged(
+    network::mojom::ConnectionType type) {
+  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
+  content::BrowserThread::PostTask(
+      content::BrowserThread::IO, FROM_HERE,
+      base::BindOnce(&PrivetTrafficDetector::HandleConnectionChanged,
+                     weak_ptr_factory_.GetWeakPtr(), type));
 }
 
-void PrivetTrafficDetector::OnNetworkChanged(
-    net::NetworkChangeNotifier::ConnectionType type) {
+void PrivetTrafficDetector::HandleConnectionChanged(
+    network::mojom::ConnectionType type) {
   DCHECK_CURRENTLY_ON(content::BrowserThread::IO);
   restart_attempts_ = kMaxRestartAttempts;
-  if (type != net::NetworkChangeNotifier::CONNECTION_NONE)
+  if (type != network::mojom::ConnectionType::CONNECTION_NONE) {
     ScheduleRestart();
+  }
 }
 
 void PrivetTrafficDetector::ScheduleRestart() {

chrome/browser/printing/cloud_print/privet_traffic_detector.h

@@ -11,9 +11,9 @@
 #include "base/cancelable_callback.h"
 #include "base/macros.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/network_connection_tracker.h"
 #include "net/base/address_family.h"
 #include "net/base/ip_endpoint.h"
-#include "net/base/network_change_notifier.h"
 
 namespace net {
 class DatagramServerSocket;
@@ -28,13 +28,15 @@ namespace cloud_print {
 // When traffic is detected, class fires callback and shutdowns itself.
 class PrivetTrafficDetector
     : public base::RefCountedThreadSafe<
-          PrivetTrafficDetector, content::BrowserThread::DeleteOnIOThread>,
-      private net::NetworkChangeNotifier::NetworkChangeObserver {
+          PrivetTrafficDetector,
+          content::BrowserThread::DeleteOnIOThread>,
+      private content::NetworkConnectionTracker::NetworkConnectionObserver {
  public:
   PrivetTrafficDetector(net::AddressFamily address_family,
                         const base::Closure& on_traffic_detected);
 
   void Start();
+  void Stop();
 
  private:
   friend struct content::BrowserThread::DeleteOnThread<
@@ -42,11 +44,10 @@ class PrivetTrafficDetector
   friend class base::DeleteHelper<PrivetTrafficDetector>;
   ~PrivetTrafficDetector() override;
 
-    // net::NetworkChangeNotifier::NetworkChangeObserver implementation.
-  void OnNetworkChanged(
-      net::NetworkChangeNotifier::ConnectionType type) override;
+  // content::NetworkConnectionTracker::NetworkConnectionObserver:
+  void OnConnectionChanged(network::mojom::ConnectionType type) override;
 
-  void StartOnIOThread();
+  void HandleConnectionChanged(network::mojom::ConnectionType type);
   void ScheduleRestart();
   void Restart(const net::NetworkInterfaceList& networks);
   int Bind();