WebRTC

• Added WebRTC options to the Developer menu
• Disabled Legacy WebRTC API in the Experimental Features menu by default (r218169)
• Changed behavior to close NetworkProcess WebRTC sockets as soon as the Web Process no longer needs them (r218432)
• Added support for receive-only SDP offers through addTransceiver (r218431)
• Changed handling capture status based on MediaStreamTrack (r218399)
• Changed RTCPeerConnection to return RTCSessionDescriptionInit instead of RTCSessionDescription (r218335)
• Fixed a cloned MediaStreamTrack to not mute the other tracks using the same source (r218497)
• Fixed RTCPeerConnection getReceivers() to return transceivers that have an active receiver but no active sender (r218182)
• Fixed the screen going into sleep mode during WebRTC video (r218151)

Media

• Fixed high CPU usage when entering fullscreen or seeking during MSE video playback (r218463)
• Fixed seeking during MSE video playback where audio would begin playing long before rendering the video (r218150)
• Fixed video flashing black when switching back to a tab (r218291)
• Improved media controls rendering for long-loading media files (r218600)
• Prevented media elements continuing to load media data after navigation (r218016)

JavaScript

• Made Object.assign faster by rewriting it in C++ (r218348)
• Reduced Structure size (r218070)
• Updated RegExp.prototype.[@@search]] implementation according to the latest specifications (r218051)
• Fixed PreTypedArray constructor with a string to not throw an exception (r218082)

Security

• Applied img-src CSP directive to favicon loads (r218015, r218026)
• Implemented W3C Secure Contexts Draft Specification (r218027, r218028, r218155, r218196)
• Restricted filtered painting across cross-origin boundaries with transforms (r218300)
• Added allow-popups-to-escape-sandbox attribute support for <iframe> elements (r218000)
• Added Subresource Integrity as an experimental feature (r217996)

Web Inspector

• Added grid to image previews to clarify transparency and image size (r218159)
• Fixed console message icons that overlap the source location (r218243)
• Fixed pretty print, type info, and code coverage buttons disappearing after switching tabs (r218305)
• Fixed SVG files and favicon files that don’t display properly (r218298)
• Fixed the search highlight not showing up in resources when paused (r218359)
• Fixed showing non-shadow children of an element with a shadow root (e.g. <video>) (r218020)

Web API

• Fixed the meter element not respecting the writing direction (r218468)
• Fixed WebGPU contexts to have a back reference to the canvas element (r218624)
• Fixed CSS transitions added while page is not visible so they start animating when the page becomes visible (r217997)
• Fixed IndexedDB.getAll() use inside a Web Worker (r218041)

WebCrypto

• Moved SubtleCrypto from the experiemental features menu (r218129)
• Removed unsupported AES_CMAC, DH, and CONCAT (r218030)

WebAssembly

• Fixed several miscellaneous bugs found from web platform tests (r218216)

Rendering

• Added an experimental feature setting for asynchronous frame scrolling (r218534)

Accessibility

• Exposed the inline property as an accessibility attribute (r218226)

Bug Fixes

• Fixed mint.com header rendering incorrectly when initially loaded (r218257)
• Fixed scrubbing backward on a YouTube video