Pull web-animations-js into third-party via the third_party/polymer/reproduce.sh script. Add necess…

third_party/web-animations-js/sources/README.md

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+
+Quick Start
+-----------
+
+To provide native Chrome Web Animation features (`Element.animate` and Playback
+Control) in other browsers, use `web-animations.min.js`. To explore all of the
+proposed Web Animations API, use `web-animations-next.min.js`.
+
+What is Web Animations?
+-----------------------
+
+Web Animations is a new JavaScript API for driving animated content on the web.
+By unifying the animation features of SVG and CSS, Web Animations unlocks
+features previously only usable declaratively, and exposes powerful,
+high-performance animation capabilities to developers.
+
+For more details see the
+[W3C specification](http://w3c.github.io/web-animations/).
+
+What is the polyfill?
+---------------------
+
+The polyfill is a JavaScript implementation of the Web Animations API. It works
+on modern versions of all major browsers. For more details about browser
+support see <https://www.polymer-project.org/resources/compatibility.html>.
+
+Getting Started
+---------------
+
+Here's a simple example of an animation that scales and changes the opacity of
+a `<div>` over 0.5 seconds. The animation alternates producing a pulsing
+effect.
+
+    <script src="web-animations.min.js"></script>
+    <div class="pulse" style="width:150px;">Hello world!</div>
+    <script>
+        var elem = document.querySelector('.pulse');
+        var player = elem.animate([
+            {opacity: 0.5, transform: "scale(0.5)"},
+            {opacity: 1.0, transform: "scale(1)"}
+        ], {
+            direction: 'alternate',
+            duration: 500,
+            iterations: Infinity
+        });
+    </script>
+
+Web Animations supports off-main-thread animations, and also allows procedural
+generation of animations and fine-grained control of animation playback. See
+<http://web-animations.github.io> for ideas and inspiration!
+
+Native Fallback
+---------------
+
+When the polyfill runs on a browser that implements Element.animate and
+AnimationPlayer Playback Control it will detect and use the underlying native
+features.
+
+Different Build Targets
+-----------------------
+
+### web-animations.min.js
+
+Tracks the Web Animations features that are supported natively in browsers.
+Today that means Element.animate and Playback Control in Chrome. If you’re not
+sure what features you will need, start with this.
+
+### web-animations-next.min.js
+
+Contains all of web-animations.min.js plus features that are still undergoing
+discussion or have yet to be implemented natively.
+
+### web-animations-next-lite.min.js
+
+A cut down version of web-animations-next, it removes several lesser used
+property handlers and some of the larger and less used features such as matrix
+interpolation/decomposition.
+
+### Build Target Comparison
+
+|                        | web-animations | web-animations-next | web-animations-next-lite |
+|------------------------|:--------------:|:-------------------:|:------------------------:|
+|Size (gzipped)          | 12.5kb         | 14kb                | 10.5kb                   |
+|Element.animate         | ✔             | ✔                  | ✔                       |
+|Timing input (easings, duration, fillMode, etc.) for animations| ✔ | ✔ | ✔             | 
+|Playback control        | ✔             | ✔                  | ✔                       |
+|Support for animating lengths, transforms and opacity| ✔ | ✔ | ✔                       |
+|Support for Animating other CSS properties| ✔ | ✔            | 🚫                       |
+|Matrix fallback for transform animations | ✔ | ✔             | 🚫                       |
+|Animation constructor   | 🚫             | ✔                  | ✔                       |
+|Simple Groups           | 🚫             | ✔                  | ✔                       |
+|Custom Effects          | 🚫             | ✔                  | ✔                       |
+|Timing input (easings, duration, fillMode, etc.) for groups</div>| 🚫 | 🚫\* | 🚫         |
+|Additive animation      | 🚫             | 🚫\*                | 🚫                       |
+|Motion path             | 🚫\*           | 🚫\*                | 🚫                       |
+|Modifiable animation timing| 🚫          | 🚫\*                | 🚫\*                     |
+|Modifiable group timing | 🚫             | 🚫\*                | 🚫\*                     |
+|Usable inline style\*\* | ✔             | ✔                  | 🚫                       |
+
+\* support is planned for these features.
+\*\* see inline style caveat below.
+
+Caveats
+-------
+
+Some things won’t ever be faithful to the native implementation due to browser
+and CSS API limitations. These include:
+
+### Inline Style
+
+Inline style modification is the mechanism used by the polyfill to animate
+properties. Both web-animations and web-animations-next incorporate a module
+that emulates a vanilla inline style object, so that style modification from
+JavaScript can still work in the presence of animations. However, to keep the
+size of web-animations-next-lite as small as possible, the style emulation
+module is not included. When using this version of the polyfill, JavaScript
+inline style modification will be overwritten by animations.
+Due to browser constraints inline style modification is not supported on iOS 7
+or Safari 6 (or earlier versions).
+
+### Prefix handling
+
+The polyfill will automatically detect the correctly prefixed name to use when
+writing animated properties back to the platform. Where possible, the polyfill
+will only accept unprefixed versions of experimental features. For example:
+
+    var animation = new Animation(elem, {"transform": "translate(100px, 100px)"}, 2000);
+
+will work in all browsers that implement a conforming version of transform, but
+
+    var animation = new Animation(elem, {"-webkit-transform": "translate(100px, 100px)"}, 2000);
+
+will not work anywhere.
+
+API and Specification Feedback
+------------------------------
+
+File an issue on GitHub: <https://github.com/w3c/web-animations/issues/new>.
+Alternatively, send an email to <public-fx@w3.org> with subject line
+“[web-animations] … message topic …”
+([archives](http://lists.w3.org/Archives/Public/public-fx/)).
+
+Polyfill Issues
+---------------
+
+Report any issues with this implementation on GitHub:
+<https://github.com/web-animations/web-animations-next/issues/new>.
+
+Breaking changes
+----------------
+
+When we make a potentially breaking change to the polyfill's API
+surface (like a rename) where possible we will continue supporting the
+old version, deprecated, for three months, and ensure that there are
+console warnings to indicate that a change is pending. After three
+months, the old version of the API surface (e.g. the old version of a
+function name) will be removed. *If you see deprecation warnings you
+can't avoid it by not updating*.
+
+We also announce anything that isn't a bug fix on
+[web-animations-changes@googlegroups.com](https://groups.google.com/forum/#!forum/web-animations-changes).