Tests for font loading data collection in ResourceLoadStatistics plist by loading fonts and dumping the entire resource load statistics map. The test tries to load various fonts through a comma separated font-family list to draw a string with many m's since they differ in width more prominently among fonts.

mmmmmmmmmmlli
Resource load statistics:

High level domain: 127.0.0.1
    lastSeen: 0
    hadUserInteraction: No
    mostRecentUserInteraction: -1
    grandfathered: No
    isPrevalentResource: No
    isVeryPrevalentResource: No
    dataRecordsRemoved: 0
    fontsFailedToLoad:
        Fransiscan
        Andale
        notARealFont
    fontsSuccessfullyLoaded:
        Times
    topFrameRegistrableDomainsWhichAccessedWebAPIs:
        127.0.0.1: 5
    canvasReadData: No