[Webkit-unassigned] [Bug 134208] New: Reduce synchronous layout triggered by JavaScript-based media controls

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=134208

           Summary: Reduce synchronous layout triggered by
                    JavaScript-based media controls
           Product: WebKit
           Version: 412.x
          Platform: Unspecified
        OS/Version: Unspecified
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: WebCore Misc.
        AssignedTo: webkit-unassigned at lists.webkit.org
        ReportedBy: joepeck at webkit.org
                CC: dino at apple.com, akling at apple.com, jer.noble at apple.com


JavaScript-based media controls are triggering synchronous layout potentially multiple times during page loads with media elements. This causes unnecessary work during page loads. 

Specifically, the Apple and iOS media controls updateProgress methods, querying the offsetWidth/offsetHeight of the timeline:

>    updateProgress: function() {
>        Controller.prototype.updateProgress.call(this);
>
>        var width = this.controls.timeline.offsetWidth;
>        var height = this.controls.timeline.offsetHeight;
>        ...
>    }

During a normal page load of a <video controls url="..."> this gets triggered 8 times. We should be able to reduce that.

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