Extend TwoClientExtensionSettingsSyncTest to test app settings.

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

Index: chrome/browser/sync/test/integration/apps_helper.h
diff --git a/chrome/browser/sync/test/integration/apps_helper.h b/chrome/browser/sync/test/integration/apps_helper.h
index c7faae0b5f58209bd7918c912c5f121892f1a792..f42acf5aeb626e86c5416f81bc3a19b27350cb50 100644
--- a/chrome/browser/sync/test/integration/apps_helper.h
+++ b/chrome/browser/sync/test/integration/apps_helper.h
@@ -26,6 +26,10 @@ bool AllProfilesHaveSameAppsAsVerifier() WARN_UNUSED_RESULT;
 // ID of the new app.
 std::string InstallApp(Profile* profile, int index);
 
+// Installs the app for the given index to all profiles (including the
+// verifier), and returns the extension ID of the new app.
+std::string InstallAppForAllProfiles(int index);
+
 // Uninstalls the app for the given index from |profile|. Assumes that it was
 // previously installed.
 void UninstallApp(Profile* profile, int index);