Web Inspector: Show layout/paint pixel area in the Rendering Frames tree outline

Web Inspector: Show layout/paint pixel area in the Rendering Frames tree outline
https://bugs.webkit.org/show_bug.cgi?id=148674

Reviewed by Brian Burg.

* Localizations/en.lproj/localizedStrings.js:
New UI string.

* UserInterface/Views/RenderingFrameTimelineView.css:
(.sidebar > .panel.navigation.timeline.timeline-recording-content-view-showing .navigation-sidebar-panel-content-tree-outline.rendering-frame .item:not(.paint-record):not(.layout-record) .subtitle):
(.sidebar > .panel.navigation.timeline.timeline-recording-content-view-showing .navigation-sidebar-panel-content-tree-outline.rendering-frame .item .subtitle): Deleted.
Show subtitles for layout and paint records only. We still want to hide script record subtitles,
since that information is already in the 'Location' column.

* UserInterface/Views/RenderingFrameTimelineView.js:
(WebInspector.RenderingFrameTimelineView.prototype._processPendingRecords):
Add tree element subtitle for LayoutTimelineRecords that specify width and height.

git-svn-id: https://svn.webkit.org/repository/webkit/trunk@189236 268f45cc-cd09-0410-ab3c-d52691b4dbfc