Revert "Remove UninstallArcApps method from add supervision API"

Only rollback the changes to arc_app_utils.*, which it turns out we need
in another in-flight CL:
https://chromium-review.googlesource.com/c/chromium/src/+/1606571

This reverts part of commit 7e1d0290.

Bug: 937995
Change-Id: Id8df13e94019fea5b07da6f8d03fea8a736d6be4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1637646Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Commit-Queue: Danan S <danan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665024}

chrome/browser/ui/app_list/arc/arc_app_utils.cc

@@ -639,6 +639,12 @@ std::string AppIdToArcPackageName(const std::string& app_id, Profile* profile) {
   return app_info->package_name;
 }
 
+std::string ArcPackageNameToAppId(const std::string& package_name,
+                                  Profile* profile) {
+  ArcAppListPrefs* arc_prefs = ArcAppListPrefs::Get(profile);
+  return arc_prefs->GetAppIdByPackageName(package_name);
+}
+
 bool IsArcAppSticky(const std::string& app_id, Profile* profile) {
   ArcAppListPrefs* arc_prefs = ArcAppListPrefs::Get(profile);
   std::unique_ptr<ArcAppListPrefs::AppInfo> app_info =

chrome/browser/ui/app_list/arc/arc_app_utils.h

@@ -189,6 +189,11 @@ void GetAndroidId(
 // be the AppID of an ARC app.
 std::string AppIdToArcPackageName(const std::string& app_id, Profile* profile);
 
+// Returns the AppID for the specified package_name, which must be the package
+// name of an ARC app.
+std::string ArcPackageNameToAppId(const std::string& package_name,
+                                  Profile* profile);
+
 // Returns true if the ARC app is sticky (not uninstallable). This function
 // will DCHECK if app_id isn't installed. This functionality should eventually
 // move to the App Service: (https://crbug.com/948408).