Network panel is recalculating styles for ages. Open standalone front-end and execute for (var i = 0; i < 1000; ++i) WebInspector.networkManager._dispatcher.didLoadResourceFromMemoryCache(new Date().getTime(), {url:"foo", response: {}, loader: { url: "foo" }}); in the console. It'll fill network panel with 1K entries. Now try switching to/from panel. Also try showing resource content and closing it. You will see 600ms delay upon panel switch and 2s delay upon resource content close. We need to split content using iframes, but this is a long road. This patch will improve things a lot in the short term.
Created attachment 80591 [details] Patch
Comment on attachment 80591 [details] Patch View in context: https://bugs.webkit.org/attachment.cgi?id=80591&action=review > Source/WebCore/inspector/front-end/NetworkPanel.js:1032 > + _onScroll: function(e) I prefer "_didScroll" or "_updateOffscreenRows" over the generic "onScroll".
Committed r77127: <http://trac.webkit.org/changeset/77127>