rebuildDependencyGraphAsync can wait a fraction of a second to improve the chances that events will be coalesced.
Noting yet another weird problem with BuildTrigger’s reliance on DependencyGraph for its own execution.
Since this is now (1.522) updated asynchronously, the value may not actually be correct, potentially causing erratic behavior especially in tests.
Fingerprinter calls rebuildDependencyGraphAsync, so since this is now delayed by 500msec, tests incorrect as of 1.522 will now fail pretty reliably unless made to forcibly rebuild the graph.
Merge commit 'fd97a2f5e858ae137935dcf56d3a95b74ba279fc'