New features in WebKit trunk

Memory allocation

• New memory allocator bmalloc is now used instead of tcmalloc

JavaScriptCore

• Fetch API
• Nearly complete ES6 support (https://webkit.org/blog/4054/es6-in-webkit/), including proper tail calls
• JavaScript now uses C stack
• FTL/B3 - new JIT tier providing more aggressive optimizations than DFG JIT (currenly available only for x86_64)
• More optimizations for ASM.js code
• WebAssembly support is in development
• Various performance improvements
• Improved Inspector and other tooling

WebCore

• JIT for CSS selectors (https://webkit.org/blog/3271/webkit-css-selector-jit-compiler/)
• Various new web standards are now supported in GStreamer MediaPlayer implementation: MediaSource, MediaStream (WebRTC), WebAudio, element.
• Content Blocking API (https://webkit.org/blog/3476/content-blockers-first-look/)