[Webkit-unassigned] [Bug 77278] New: Web Inspector: revalidated cached scripts have misleading receive/parse times in Timeline

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=77278

           Summary: Web Inspector: revalidated cached scripts have
                    misleading receive/parse times in Timeline
           Product: WebKit
           Version: 528+ (Nightly build)
          Platform: All
        OS/Version: All
            Status: UNCONFIRMED
          Severity: Normal
          Priority: P2
         Component: Web Inspector
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: burg at cs.washington.edu
                CC: timothy at apple.com, rik at webkit.org, keishi at webkit.org,
                    pmuellr at yahoo.com, joepeck at webkit.org,
                    pfeldman at chromium.org, yurys at chromium.org,
                    bweinstein at apple.com, apavlov at chromium.org,
                    loislo at chromium.org


Created an attachment (id=124439)
 --> (https://bugs.webkit.org/attachment.cgi?id=124439&action=review)
ga.js is reported as parsed, executed before it is received

Revalidated (304) cached scripts will be parsed and executed before they show as being received in the Timeline panel. This does not affect normal resource loads.

After some investigation, the problem seems to be that cached resource clients are being notified of revalidation before ResourceLoader clients are being notified of the response being received. The latter can trigger parsing and execution if the cache client happens to be the document parser. I'm unsure how to fix this, since there seem to be a lot of subtle invariants in the resource loading code.

I've attached a screenshot demonstrating the incorrect timeline pill ordering, as well as a useful stack trace which seems to show the start of problems.

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