cros: Use guest profile in AppListSyncableService

In guest session, we use two different profiles for "Suggested App" and
apps in Launcher. The later uses the profile of AppListSyncableService
which alwasy uses the original profile. However, the original profile is
not allowed in guest session.

This cl fixes this bug by returning guest profile in
AppListSyncableService in guest mode.

Bug: 840293
Test: manual.
Change-Id: I30d9464597eaacba9a08560ca03e0679a9e906bf
Reviewed-on: https://chromium-review.googlesource.com/1049005
Commit-Queue: Tao Wu <wutao@chromium.org>
Reviewed-by: Xiyuan Xia <xiyuan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557014}

chrome/browser/ui/app_list/app_list_syncable_service.cc

@@ -903,6 +903,13 @@ syncer::SyncError AppListSyncableService::ProcessSyncChanges(
   return syncer::SyncError();
 }
 
+void AppListSyncableService::Shutdown() {
+  internal_apps_builder_.reset();
+  crostini_apps_builder_.reset();
+  arc_apps_builder_.reset();
+  apps_builder_.reset();
+}
+
 // AppListSyncableService private
 
 bool AppListSyncableService::ProcessSyncItemSpecifics(

chrome/browser/ui/app_list/app_list_syncable_service.h

@@ -162,6 +162,9 @@ class AppListSyncableService : public syncer::SyncableService,
       const base::Location& from_here,
       const syncer::SyncChangeList& change_list) override;
 
+  // KeyedService
+  void Shutdown() override;
+
  private:
   class ModelUpdaterDelegate;
 

chrome/browser/ui/app_list/app_list_syncable_service_factory.cc

@@ -86,6 +86,19 @@ void AppListSyncableServiceFactory::RegisterProfilePrefs(
 
 content::BrowserContext* AppListSyncableServiceFactory::GetBrowserContextToUse(
     content::BrowserContext* context) const {
+  Profile* const profile = Profile::FromBrowserContext(context);
+  // No service if |context| is not a profile.
+  if (!profile)
+    return nullptr;
+
+  // No service for system profile.
+  if (profile->IsSystemProfile())
+    return nullptr;
+
+  // Use profile as-is for guest session.
+  if (profile->IsGuestSession())
+    return chrome::GetBrowserContextOwnInstanceInIncognito(context);
+
   // This matches the logic in ExtensionSyncServiceFactory, which uses the
   // orginal browser context.
   return chrome::GetBrowserContextRedirectedInIncognito(context);