Via bug 145324 "Web Inspector: Large repaints when typing any character in console" The low hanging fruit is to convert #toolbar, #tab-bar, and #main from flexbox to position absolute. This takes the toolbar and the tab bar out of the repaint area when typing in the console or editing a resource.
<rdar://problem/25125476>
Created attachment 273806 [details] Patch I'll revisit this when bug 145324 is fixed.
Created attachment 273808 [details] [Animated GIF] With the patch applied
Created attachment 273809 [details] Patch
Comment on attachment 273809 [details] Patch Clearing flags on attachment: 273809 Committed r198065: <http://trac.webkit.org/changeset/198065>
All reviewed patches have been landed. Closing bug.