Firefox 35 for developers
=========================

Firefox 35 was released on January 13th, 2015. This article lists key changes that are useful not only for web developers, but also Firefox and Gecko developers as well as add-on developers.

Changes for Web developers
--------------------------

### Developer Tools

Highlights:

* See ::before and ::after pseudo elements in the Page Inspector
* CSS source maps are now enabled by default
* "Show DOM Properties" from the Page Inspector

All devtools bugs fixed between Firefox 34 and Firefox 35.

### CSS

* The `mask-type` property has been activated by default (Firefox bug 1058519).
* The `filter` property is now activated by default (Firefox bug 1057180).
* The `@font-face` at-rule now supports WOFF2 fonts (Firefox bug 1064737).
* The `symbols()` functional notation is now supported (Firefox bug 966168).
* The CSS Font Loading API has been implemented (Firefox bug 1028497).
* Using `-moz-appearance` with the `none` value on a combobox now remove the dropdown button (Firefox bug 649849).
* The property accessor `element.style["css-property-name"]` has been added to match other browsers (Firefox bug 958887).
### HTML

* The obsolete and non-conforming `bottommargin`, `leftmargin`, `rightmargin` and `topmargin` attributes of the `<body>` element have been activated in non-quirks mode (Firefox bug 95530).
### JavaScript

* The "temporal dead zone" for `let` declarations has been implemented. In conformance with ES2015 `let` semantics, the following situations now throw errors. See also this newsgroup announcement and Firefox bug 1001090.
    + Redeclaring existing variables or arguments using `let` within the same scope in function bodies is now a syntax error.
    + Using a variable declared using `let` in function bodies before the declaration is reached and evaluated is now a runtime error.
* ES2015 `Symbols` (only available in the Nightly channel) have been updated to conform with recent specification changes:
    + `String(Symbol("1"))` now no longer throws a `TypeError`; instead a string (`"Symbol(1)"`) gets returned (Firefox bug 1058396).
* The various *TypedArray* constructors now have as their `[[Prototype]]` a single function, denoted `%TypedArray%` in ES2015 (but otherwise not directly exposed). Each typed array prototype now inherits from `%TypedArray%.prototype`. (`%TypedArray%` and `%TypedArray%.prototype` inherit from `Function.prototype` and `Object.prototype`, respectively, so that typed array constructors and instances still have the properties found on those objects.) Typed array function properties now reside on `%TypedArray%.prototype` and work on any typed array. See *TypedArray* and Firefox bug 896116 for more information.
* ES2015 semantics for prototype mutations using object literals have been implemented (Firefox bug 1061853).
    + Now only a single member notated as `__proto__:value` will mutate the `[[Prototype]]` in the object literal syntax.
    + Method members like `__proto__() {}` will not overwrite the `[[Prototype]]` anymore.
### Interfaces/APIs/DOM

* `navigator.language` and `navigator.languages` are now available to workers on `WorkerNavigator` (Firefox bug 925849).
* The `Element.closest()` method returns the closest ancestor of the current element (Firefox bug 1055533).
* Experimental support for the `CanvasRenderingContext2D.filter` property has been added behind the `canvas.filters.enabled` flag (Firefox bug 927892).
* Our experimental implementation of Web Animations progresses with the landing of the `Animation.target` property. This always is behind the `dom.animations-api.core.enabled` pref, off by default (Firefox bug 1067701).
* The `hasAttributes()` method has been moved from `Node` to `Element` as required by the spec (Firefox bug 1055773).
* The `crossOrigin` reflected attribute of `HTMLImageElement`, `HTMLLinkElement`, `HTMLMediaElement`, `HTMLScriptElement`, and `SVGScriptElement` only accepts valid values, and `""` isn't, `null` has to be used instead (Firefox bug 880997).
* The Resource Timing API has been activated by default (Firefox bug 1002855).
* To match the spec, the first argument of `Selection.containsNode()` cannot be `null` anymore (Firefox bug 1068058).
* The new `ImageCapture` API has been implemented: `ImageCapture.takePhoto()` is available (Firefox bug 916643).
* Non-HTTP `XMLHttpRequest` requests now return `200` in case of success (instead of the erroneous `0`) (Firefox bug 716491).
* `XMLHttpRequest.responseURL` has been adapted to the latest spec and doesn't include the fragment (`'#xyz'`) of the URL, if relevant (Firefox bug 1073882).
* The internal, non-standard, `File.mozFullPath` property is no more visible from content (Firefox bug 1048293).
* The constructor of `File` has been extended to match the specification (Firefox bug 1047483).
* An experimental implementation of `AbortablePromise`, a promise that can be aborted by a different entity that the one who created it, has been added. It is prefixed with `Moz` and controlled by the `dom.abortablepromise.enabled` property, defaulting to `false` (Firefox bug 1035060).
* The non-standard `Navigator.mozIsLocallyAvailable` property has been removed (Firefox bug 1066826).
* The preference `network.websocket.enabled`, `true` by default, has been removed; Websocket API cannot be deactivated anymore (Firefox bug 1091016).
* The non-standard methods and properties of `Crypto` have been removed (Firefox bug 1030963). Only methods and properties defined in the standard WebCrypto API are left.
* Our experimental implementation of WebGL 2.0 is going forward!
    + The `WebGL2RenderingContext.copyBufferSubData()` method has been implemented (Firefox bug 1048668).
### MathML

* The `dtls` OpenType feature (via the CSS `font-feature-settings` on the default stylesheet) is now applied automatically to MathML elements when positioning scripts over it (e.g. dotless i with mathematical hat).
### SVG

*No change.*

### Audio/Video

*No change.*

Network & Security
------------------

* HTTP/2 has been implemented and activated, with AEAD ciphers only (Firefox bug 1027720 and Firefox bug 1047594).
* The HTTP/2 `alt-svc` header is now supported (Firefox bug 1003448).
* The Public Key Pinning Extension for HTTP (HPKP) has been implemented (Firefox bug 787133).
* The CSP 1.1 `base-uri` directive is now supported (Firefox bug 1045897).
* Path of the source is now considered too when host-source matching happens in CSP (Firefox bug 808292).
Changes for add-on and Mozilla developers
-----------------------------------------

### XUL & Add-ons

* The private `_getTabForBrowser()` method on the `<xul:tabbrowser>` element has been deprecated. In its place, we've added a new, public, method called `getTabForBrowser`. This returns, predictably, the `<xul:tab>` element that contains the specified `<xul:browser>`.
* `Components.utils.now()`, matching `Performance.now()` has been implemented for non-window chrome code (Firefox bug 969490).
### Add-on SDK

#### Highlights

* Added access keys for context menu.
* Removed `isPrivateBrowsing` from `BrowserWindow`.
* Added `toJSON` method to `URL` instances.

#### Details

GitHub commits made between Firefox 34 and Firefox 35. This will not include any uplifts made after this release entered Aurora.

Bugs fixed between Firefox 34 and Firefox 35. This will not include any uplifts made after this release entered Aurora.

Older versions
--------------

* Firefox 34 for developers
* Firefox 33 for developers
* Firefox 32 for developers
* Firefox 31 for developers
* Firefox 30 for developers
* Firefox 29 for developers
* Firefox 28 for developers
* Firefox 27 for developers
* Firefox 26 for developers
* Firefox 25 for developers
* Firefox 24 for developers
* Firefox 23 for developers
* Firefox 22 for developers
* Firefox 21 for developers
* Firefox 20 for developers
* Firefox 19 for developers
* Firefox 18 for developers
* Firefox 17 for developers
* Firefox 16 for developers
* Firefox 15 for developers
* Firefox 14 for developers
* Firefox 13 for developers
* Firefox 12 for developers
* Firefox 11 for developers
* Firefox 10 for developers
* Firefox 9 for developers
* Firefox 8 for developers
* Firefox 7 for developers
* Firefox 6 for developers
* Firefox 5 for developers
* Firefox 4 for developers
* Firefox 3.6 for developers
* Firefox 3.5 for developers
* Firefox 3 for developers
* Firefox 2 for developers
* Firefox 1.5 for developers