Implement OnNetworkChangeObserver interface on SmbService

- Implements Net::NetworkChangeNotifier::NetworkChangeObserver to
  SmbService.
- Optimizes the workflow of host name resolution by calling on host
  discovery whenever a network change is discovered, rather than
  only running host discovery on an error returned by
  StartReadDirectory.

Bug: 922273
Test: manual end to end
Change-Id: I9e91a1527fe06570b3d82c7abc92c448c07ed74a
Reviewed-on: https://chromium-review.googlesource.com/c/1484501
Commit-Queue: jimmy gong <jimmyxgong@chromium.org>
Reviewed-by: Bailey Berro <baileyberro@chromium.org>
Cr-Commit-Position: refs/heads/master@{#635203}

chrome/browser/chromeos/smb_client/smb_service.cc

@@ -121,7 +121,9 @@ SmbService::SmbService(Profile* profile,
   }
 }
 
-SmbService::~SmbService() {}
+SmbService::~SmbService() {
+  net::NetworkChangeNotifier::RemoveNetworkChangeObserver(this);
+}
 
 // static
 SmbService* SmbService::Get(content::BrowserContext* context) {
@@ -525,6 +527,7 @@ void SmbService::CompleteSetup(
       base::BindRepeating(&SmbService::RequestUpdatedSharePath,
                           base::Unretained(this))));
   RestoreMounts();
+  net::NetworkChangeNotifier::AddNetworkChangeObserver(this);
 }
 
 void SmbService::FireMountCallback(MountResponse callback,
@@ -662,6 +665,22 @@ bool SmbService::ShouldRunHostDiscoveryAgain() const {
          previous_host_discovery_time_ + kHostDiscoveryInterval;
 }
 
+void SmbService::OnNetworkChanged(
+    net::NetworkChangeNotifier::ConnectionType type) {
+  user_manager::User* user =
+      chromeos::ProfileHelper::Get()->GetUserByProfile(profile_);
+
+  if (!user) {
+    // If a network change occurs on the lockscreen, do nothing.
+    return;
+  }
+
+  // Run host discovery to refresh list of cached hosts for subsequent name
+  // resolution attempts.
+  share_finder_->DiscoverHostsInNetwork(base::DoNothing()
+                                        /* HostDiscoveryResponse */);
+}
+
 void SmbService::RecordMountCount() const {
   const std::vector<ProvidedFileSystemInfo> file_systems =
       GetProviderService()->GetProvidedFileSystemInfoList(provider_id_);

chrome/browser/chromeos/smb_client/smb_service.h

@@ -25,6 +25,7 @@
 #include "chrome/browser/profiles/profile.h"
 #include "chromeos/dbus/smb_provider_client.h"
 #include "components/keyed_service/core/keyed_service.h"
+#include "net/base/network_change_notifier.h"
 
 namespace base {
 class FilePath;
@@ -46,6 +47,7 @@ using file_system_provider::Service;
 
 // Creates and manages an smb file system.
 class SmbService : public KeyedService,
+                   public net::NetworkChangeNotifier::NetworkChangeObserver,
                    public base::SupportsWeakPtr<SmbService> {
  public:
   using MountResponse = base::OnceCallback<void(SmbMountResult result)>;
@@ -245,6 +247,11 @@ class SmbService : public KeyedService,
   // false if HostDiscovery was recently run.
   bool ShouldRunHostDiscoveryAgain() const;
 
+  // NetworkChangeNotifier::NetworkChangeObserver override. Runs HostDiscovery
+  // when network detects a change.
+  void OnNetworkChanged(
+      net::NetworkChangeNotifier::ConnectionType type) override;
+
   // Records metrics on the number of SMB mounts a user has.
   void RecordMountCount() const;