New Additions

• Rename declarations of goog.iter.Iterator#next to #nextValueOrThrow, leaving behind aliasing implementations of #next. If your codebase uses goog.iter.Iterator, similar changes should be applied to your codebase to prepare for upcoming Closure Library changes that call nextValueOrThrow where next is currently called. (00482177a4d042a0bfc4107b7fe7587ef3ccfa00)

Backwards Incompatible Changes

• Deleted goog.provide for goog.net.streams.JsonStreamParser.Options (fc26060da25c49fdc4bdbf675b615f79899c9a4e)
• Delete goog.date.formatMonthAndYear. (ed02aa9f2c6b41394d33fb64cfbea5014000775f)
• goog.editor.Field.prototype.shouldRefocusOnInputMobileSafari has been removed. (1cb5f6f0b0a0a0b3189519e2ee47447025c88cf3)
• Remove the fourth parameter passed to window.open. (5d49bd0bfce837ca002dd987b40b4411da7dfea6)
• Removed 'goog.ui.GaugeColoredRange' as a namespace. (24820b0e2e0b3551e29a1c72f8dcecb63113fca9)
• goog.structs.Map#set no longer returns a value, to align with ES6 Map. (a00c1e660a213d913cfa1d30ece2e79ddabadea0)

Other Changes

• Delete open-sourced Python helper scripts. (749634639af6b04bfe1d9d890bb037811e390b61)
• Return the correct singleton when using goog.singleton with subclassed classes. (1422c2542c30d415c05d3f2b689f302756598087)
• Small type safety fix. (9d24a6c1809a671c2e54c328897ebeae15a6d172)
• Disable failing test. (1b3935376a0f851ddf1caf1c1dc62095c025d580)
• Various type-safety fixes for closure/ui. (e40ca542aa1493211b9471ac0b8072ec27a9c205)
• Add var css function name to safestyle allowlist. (1ba22498b9cdcfe989fbc7a6b4b713742fa76563)
• Remove missingRequire suppressions (e7d2e82643b2b72eec43461c496a8fdd920fc4cd)
• One-line summary of change for external release notes. (a009a5e8c83331462ef3618c4ab8833ae88389fe)
• Remove support for IE8 and before, Gecko 3.x and before, and Safari 5.1 and before. (0bc21defc6d35a0de4c02c887416fdc8e9b0fc56, d53f6fd565bf198bd5ec6afd8ecb41571f3ca728, 8640bb4ba443cca1dc326270b299dc9c2ca02da0, 2113d7c8a16760581b115d0e6daf408ce656d5ce, 4479b9f8d0a8a16c21ca44a92a21c7035361a007, a1eee6326967209ac0a4984d915086e673a99c1e, 7f64bd1c62962cf30a8222231723e3a9637cb377, f848b52ed93f046e25e85b444216d1c2f37a702f, bb45183392a4f45310a933e34173b4953e9f000f, a6ad7d8ba438e5999afe63a45f4518c7a9cef826, 58088037accd0f275970b28c358f535334ddd25d, 9ce5d59600caa6a7b7926a713b4aa42de41ea8c6, 415d9e49e3902680cc653cb45a578f6a4aa9a603, 7a5a20cc34f1779520db2a30e3bb7522886c3c36, 0b18892d62773ad93483dc547ba7a33fe43616c2)
• Add graceful degradation for the Cobalt (https://cobalt.dev) browser. (46bbac9e9c9945af089d574fd969ec773596fffe)
• In goog.userAgent, check for "CriOS" in the user agent string when determining Chrome version on macOS. (b9885a84b20fb61358570ca1eb9c2d2d2bb46b9e)
• Round the elapsed time in the "x of y tests run in z ms" message printed by the Closure test runner. Add a space before "ms". (792a43ce71c9eb6aca3ae73c5cf8bf0de78e7257)
• Drop support for pre-Chromium Opera (c7ea3f4a00d81a3215a76f9085472e7b36166019)
• BrowserRange no longer has special cases for IE and Opera. (e510109d13c3909e4ea0a90dd48ab0443ce9a8b2)
• Replace calls to methods on goog.structs,Set that aren't present on an ES6 Set with compatible equivalent code. (47bd286a36ef5a9c49026c9d0a1428b7370185b4)