We should no longer do proxy-related IO on the main thread now that Patrick McManus landed bug 769764. Synchronous proxy code resulted in a miserable user experience for people using proxies, but it also affected normal users during proxy-detection. This was one of the top intermittent freezes that we’ve seen.
Tab switching should be much faster in Firefox 18 than before. Jared Wein got rid of an expensive regexp that was applied during a tab switch in bug 781588. Jeff Muizelaar landed bug 792199 which should make switching to a image-heavy sites much faster. Jared’s change is already on nightlies, Jeff’s change should show up tomorrow if everything goes well.
Matt Woodrow landed the huge change that is DLBI in bug 539356 (yet again). DLBI speeds up reflows, reduces repaints resulting in a more responsive browser. For more details see Robert O’Callahan’s announcement.
After working on improving startup for the last couple of releases we seem to have regressed it during the 18 cycle. I filed bug 798130 on this. I just noticed the regression a few hours ago. If anyone has ideas on what might’ve caused it, please comment.
Gecko profiler now lives on AMO.