Add local_discovery.enabled pref to control access to chrome://devices

The pref controls the local discovery UI (chrome://devices) which shows
discoverable devices near the user as well as cloud devices registered
to them. The page also allows for the adding of printers/devices, a
capability that administrators may want to restrict.

The pref defaults to true.

A future CL will add the policy configurations.

Bug: 1011582
Change-Id: I84a7ca5d22893b0a5cb0bf7948375ad8ef426288
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1975292Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Daniel Hosseinian <dhoss@chromium.org>
Cr-Commit-Position: refs/heads/master@{#726249}

chrome/browser/ui/webui/chrome_web_ui_controller_factory.cc

@@ -685,7 +685,8 @@ WebUIFactoryFunction GetWebUIFactoryFunction(WebUI* web_ui,
   }
 #endif
 #if BUILDFLAG(ENABLE_SERVICE_DISCOVERY)
-  if (url.host_piece() == chrome::kChromeUIDevicesHost) {
+  if (url.host_piece() == chrome::kChromeUIDevicesHost &&
+      profile->GetPrefs()->GetBoolean(prefs::kLocalDiscoveryEnabled)) {
     return &NewWebUI<LocalDiscoveryUI>;
   }
 #endif

chrome/browser/ui/webui/local_discovery/local_discovery_ui.cc

@@ -105,6 +105,7 @@ LocalDiscoveryUI::LocalDiscoveryUI(content::WebUI* web_ui)
 
 void LocalDiscoveryUI::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
+  registry->RegisterBooleanPref(prefs::kLocalDiscoveryEnabled, true);
   registry->RegisterBooleanPref(
       prefs::kLocalDiscoveryNotificationsEnabled,
 #if defined(OS_WIN)

chrome/common/pref_names.cc

@@ -1394,6 +1394,10 @@ const char kMessageCenterDisabledExtensionIds[] =
 // platforms.
 const char kFullscreenAllowed[] = "fullscreen.allowed";
 
+// Enable the local discovery UI (chrome://devices) which shows discoverable
+// devices near the user as well as cloud devices registered to them.
+const char kLocalDiscoveryEnabled[] = "local_discovery.enabled";
+
 // Enable notifications for new devices on the local network that can be
 // registered to the user's account, e.g. Google Cloud Print printers.
 const char kLocalDiscoveryNotificationsEnabled[] =

chrome/common/pref_names.h

@@ -446,6 +446,7 @@ extern const char kMessageCenterDisabledExtensionIds[];
 
 extern const char kFullscreenAllowed[];
 
+extern const char kLocalDiscoveryEnabled[];
 extern const char kLocalDiscoveryNotificationsEnabled[];
 
 #if defined(OS_ANDROID)