Web Inspector: Avoid recreating Timeline's DataGridNode data multiple times

[Joseph Pecoraro]

* SUMMARY
Avoid recreating Timeline's DataGridNode data multiple times

Many TimelineDataGridNode subclasses do something like:

    get data()
    {
        // some work
        return {
          ...
        };
    }

    createCellContent(columnIdentifier, cell)
    {
        // Invoke the `data` getter above to create the object...
        var value = this.data[columnIdentifier];
    }

We should avoid recreating lots of objects in data. Lets do it once and cache it.

[Radar WebKit Bug Importer]

<rdar://problem/24393701>

[Joseph Pecoraro]

Created attachment 270135 [details]
[PATCH] Proposed Fix

[WebKit Commit Bot]

Comment on attachment 270135 [details]
[PATCH] Proposed Fix

Clearing flags on attachment: 270135

Committed r195779: <http://trac.webkit.org/changeset/195779>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.