Tests for canvas read and write data collection in ResourceLoadStatistics plist by rendering and reading text on the canvas and dumping the entire resource load statistics map.
Resource load statistics:

High level domain: 127.0.0.1
    lastSeen: 0
    hadUserInteraction: No
    mostRecentUserInteraction: -1
    grandfathered: No
    isPrevalentResource: No
    isVeryPrevalentResource: No
    dataRecordsRemoved: 0
    fontsSuccessfullyLoaded:
        Helvetica
        Times
    topFrameRegistrableDomainsWhichAccessedWebAPIs:
        127.0.0.1: 4
    canvasTextWritten:
        suspicious invisible text
    canvasReadData: Yes