[Webkit-unassigned] [Bug 94070] New: [CSSRegions] broken feature detection: syntax parsing succeeds when ENABLE_CSS_REGIONS is false

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=94070

           Summary: [CSSRegions] broken feature detection: syntax parsing
                    succeeds when ENABLE_CSS_REGIONS is false
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: CSS
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: paul.irish at gmail.com
                CC: mihnea at adobe.com, mibalan at adobe.com


1. If CSS Regions is not enabled (it's turned off in about:flags in Chrome) then the following should be true

    document.body.style.webkitRegionOverflow == undefined

Currently it'll return an empty string.

2. Additionally, in http://adobe.github.com/web-platform/utilities/css-regions-support-matrix/
One of the assertions ('Initial default value for region-overflow') will pass in Chrome Canary with the flag turned off.  Chrome should score a 0 with the feature turned off.

3. With this fixed, feature detects would fail fast:
https://github.com/Modernizr/Modernizr/blob/b18048b4b4245326d7f6f5a998df58050acf51a9/feature-detects/css-regions.js#L12-17

4. More importantly, this may end up being a false positive in the upcoming @supports functionality (bug 86146)

Thanks!

(Feel free to rename ticket if I've gotten the details wrong)

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