Bug 95693 – Large file causes infinite "Recalculate Style"

• Component: Layout and Rendering
• Status: UNCONFIRMED

Created attachment 161940 [details]
2 Test Cases - includes TimelineRawData

Attached are two test cases. They were created using one simple HTML file, copied multiple times into a single file. The TimelineRawData files were created with Chrome, as the latest WebKit Nightly r127384 does not contain a "Save Timeline"-option. 

Test Case 1 (around 1,7 MB) renders in about 14 seconds in Chrome 21 and WebKit nightly r127384.
Test Case 2 (aorund 9,7 MB) was cancelled after about 20 minutes of rendering. Chrome/WebKit is unresponsive and scrolling the webpage does not work. Looking at the recorded Timeline shows a huge amount of time used to "Recalculate Styles".

This clearly has something to do with the redundant style-information provided inside the file. Stripping out all CSS information except the first one lets WebKit render the second file in about 10 seconds.

I admit that this is not a typical use-case and that the proper way to get around this "bug" (if it's even a bug) is an optimized HTML file. Sadly some companys use files like these...

IE 9 for example renders both files completely in <5 seconds.