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Last week in WebKit: Performance and unprefixed Content Security Policies

November 5th, 2012

A total of 677 patches were landed by 166 authors in WebKit last week. This update talks about them, up to revision 133432.

The version of CodeMirror Web Inspector uses, which is available as an experimental editor, has been updated to version 3. Redoing an action can now be done by typing Ctrl+Y on non-Mac platforms. Furthermore, the CPU Activity feature of the Timeline panel has been promoted out of being experimental. A native memory usage overview has been implemented as well.

Quite a few performance improvements went in last week. Elliott improved performance of getElementsByTagName, among various other tests, by several percentages. Eric has been working on addressing RoboHornet(Pro) issues: rendering tables with column groups now is twice as fast, devirtualizing first- and lastChild() yielded another 30% speedup, and another 35% improvement which lowers the total test run-time from 8.2 seconds to just 5.3!

As there is no way to set them through CSS, vertex shaders with custom attributes used by CSS Shaders are now considered invalid. The -webkit-user-select property now accepts the “all” value, and -webkit-line-break has been updated to also understand “auto”, “strict” and “loose”. Thiago landed parsing for the @-webkit-viewport rule, together with the max-zoom, min-zoom, orientation and user-zoom CSS properties and their validation.

WebKit’s Content Security Policy implementation will now listen to unprefixed Content-Security-Policy headers included in the HTTP response. This header will be preferred to X-WebKit-CSP, which still must be used in case you’re supplying CSP 1.1 features to the browser. Development of the cross-site scripting protection has been picked up again. Malformed headers will now be reported, and report URLs can now be defined in the X-XSS-Protection header.

Other changes which occurred last week: