The following was missing:

settings.setDomStorageEnabled(true);

setDatabasePath() method was deprecated in API level 19. I advise you to use storage locale like this:

webView.getSettings().setDomStorageEnabled(true);
webView.getSettings().setDatabaseEnabled(true);
if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {
    webView.getSettings().setDatabasePath("/data/data/" + webView.getContext().getPackageName() + "/databases/");
}

I've also had problem with data being lost after application is restarted. Adding this helped:

webView.getSettings().setDatabasePath("/data/data/" + webView.getContext().getPackageName() + "/databases/");

A solution that works on my Android 4.2.2, compiled with build target Android 4.4W:

WebSettings settings = webView.getSettings();
settings.setDomStorageEnabled(true);
settings.setDatabaseEnabled(true);

if (Build.VERSION.SDK_INT < Build.VERSION_CODES.KITKAT) {
    File databasePath = getDatabasePath("yourDbName");
    settings.setDatabasePath(databasePath.getPath());
}

If your app use multiple webview you will still have troubles : localStorage is not correctly shared accross all webviews.

If you want to share the same data in multiple webviews the only way is to repair it with a java database and a javascript interface.

This page on github shows how to do this.

hope this help!