Revert of Unpack theme data from extensions off of UI thread.

chrome/browser/sync/test/integration/sync_integration_test_util.h

Index: chrome/browser/sync/test/integration/sync_integration_test_util.h
diff --git a/chrome/browser/sync/test/integration/sync_integration_test_util.h b/chrome/browser/sync/test/integration/sync_integration_test_util.h
index 63df4c976f76ffbbf2f508105d7f99eb4ff06c6a..c3af2d76cbceb07419832d9dc463e25eb6e2e4b1 100644
--- a/chrome/browser/sync/test/integration/sync_integration_test_util.h
+++ b/chrome/browser/sync/test/integration/sync_integration_test_util.h
@@ -11,14 +11,9 @@
 #include "chrome/browser/sync/test/integration/single_client_status_change_checker.h"
 #include "components/sync/base/model_type.h"
 
-class Profile;
-
 namespace browser_sync {
 class ProfileSyncService;
 }  // namespace browser_sync
-
-// Sets a custom theme and wait until the asynchronous process is done.
-void SetCustomTheme(Profile* profile, int theme_index = 0);
 
 // Checker to block until the server has a given number of entities.
 class ServerCountMatchStatusChecker