Version 3.5, code name Shiretoko,[25] adds a variety of new features to Firefox. Initially numbered Firefox 3.1, Mozilla developers decided to change the numbering of the release to 3.5, in order to reflect a significantly greater scope of changes than originally planned.[26] The final release was on June 30, 2009. The changes included much faster performance thanks to an upgrade to SpiderMonkey JavaScript engine called TraceMonkey and rendering improvements,[27] and support for the and tags as defined in the HTML5 specification, with a goal to offer video playback without being encumbered by patent problems associated with many video technologies.[28] Cross-site XMLHttpRequests (XHR), which can allow for more powerful web applications and an easier way to implement mashups, are also implemented in 3.5.[29] A new global JSON object contains native functions to efficiently and safely serialize and deserialize JSON objects, as specified by the ECMAScript 3.1 draft.[30] Full CSS 3 selector support has been added. Firefox 3.5 uses the Gecko 1.9.1 engine, which includes a few features that were not included in the 3.0 release. Multi-touch trackpad support was also added to the release, including gesture support like pinching for zooming and swiping for back and forward.[31] Firefox 3.5 also features an updated logo.[32]