commit 8702a885235aa50b603feb8b1d8d491741b4e693
author Shawn Pearce <sop@google.com> Sun May 15 21:28:58 2016 -0700
committer Shawn Pearce <sop@google.com> Sun May 15 22:21:36 2016 -0700
tree 0a4aa4db6d1ec5f4da5eca2499b215a52c30b145
parent c48cdc8a2a57e63c115cc6038da6770fe4a83d68

CurrentUser.PropertyKey<T>: allow plugins to cache data on users

This new map inside of both IdentifiedUser and AccountState allows
plugins to store their own information within a single user instance,
or the cached AccountState.

A property cache is primarily useful for an expensive AvatarProvider
that may need to lookup data based on AccountExternalIds on the
AccountState or the IdentifiedUser and reuse this for multiple
getUrl() invocations of varying image sizes.

Plugins can use it like this:

  private static final CurrentUser.PropertyKey<String> imageUrl =
      CurrentUser.PropertyKey.create();

  public String getUrl(IdentifiedUser user, int size) {
    String url = user.get(imageUrl);
    if (url == null) {
      url = "http://image.host/" + userId + "?size=";
      user.set(imageUrl, url);
    }
    return url + size;
  }

Begin using this for the notification filters, which are only used
inside of IsWatchedByPredicate, a non-common predicate. This gets
the database code out of IdentifiedUser and isolates it down to the
sole user in the query system.

Change-Id: Ica7409411eaf60af8d554c33b873c930b9abea6f