Posted by Marja Hölttä and Daniel Vogelheim, Resident Loader Coders


Code caching is another new technique that helps speed up page loading, specifically on repeated visits to the same page. Normally, the V8 engine compiles the page’s JavaScript on every visit, turning it into instructions that a processor understands. This compiled code is then discarded once a user navigates away from the page as compiled code is highly dependent on the state and context of the machine at compilation time. Chrome 42 introduces an advanced technique of storing a local copy of the compiled code, so that when the user returns to the page the downloading, parsing, and compiling steps can all be skipped. Across all page loads, this allows Chrome to avoid about 40% of compile time and saves precious battery on mobile devices.

These are two examples of ways Chrome is improving page load time, but page load time is just one way to think about the performance of the browser. Stay tuned for more ways the Chromium project is pushing forward all aspects of performance on the web.

Posted by John Mellor and Michael van Ouwerkerk, 'appiest Software Engineers in London

Push Notifications

This release includes two new APIs that together allow sites to push native notifications to their users even after the page is closed—provided the user has granted explicit permission. After the user has granted permission, a developer can use the new Push API to remotely wake up their service worker using Google Cloud Messaging. Once awake, the service worker may run JavaScript for a short period but in this release it is required at minimum to show a user-visible notification. Each notification includes a ‘Site Settings’ button, allowing users to easily disable notifications for a site.

Promoting Add to Home Screen

Chrome 32 introduced the ability for Android users to add home screen shortcuts to their favorite websites via a menu item. In this release, users who frequently visit a high-quality web app will see a banner that allows them to add the site to their home screen in one tap.

Sites that wish to take advantage of this new feature must meet eligibility criteria that ensure that users have a good experience when launching sites from the home screen, even when offline. The criteria will evolve over time based on feedback from users and developers, but today they require sites to provide a Web App Manifest, serve all content using HTTPS, and at least partially work offline using a service worker.

ES6 Classes

Developers often find it hard to adapt to JavaScript’s prototype-based inheritance and although many libraries have introduced their own patterns for emulating classes, the language hasn't yet provided a single, uniform way of describing them.

ES6 classes solve this by providing JavaScript a clean, standardized syntax for classes. This new syntax is available in Chrome 42 for JavaScript written in strict mode.

'use strict';

class Polygon {

   constructor(height, width) {

       this.name = 'Polygon';

       this.height = height;

       this.width = width;

   }

   sayName() {

       log('Hi, I am a ', this.name + '.');

   }

}

let p = new Polygon(300, 400);

Other updates in this release

• DevTools now allows developers to visually edit cubic beziers directly from the styles pane, making it easier to understand and modify animations.
• The Fetch API is now available in the window context, shared workers, and dedicated workers, providing a new promise-based standard for AJAX requests.
• The startRendering method of an OfflineAudioContext instance now returns a promise that resolves when the audio has finished rendering, making it easier to design web apps that work with the Web Audio API.
• AudioBufferSourceNode.buffer can no longer be set more than once, protecting developers from the lack of control over when the new source starts.
• Chrome OS now supports screen.orientation and fires the DeviceOrientationEvent when the device’s orientation changes significantly, allowing orientation-aware websites to operate correctly on Chrome OS devices.
• This release includes an updated and unprefixed implementation of Encrypted Media Extensions, which allows media sites to discover and interact with digital rights management systems..
• A new content setting allows users to automatically pause non-primary plugin content to save power. Developers can turn it on to test how it interacts with their content.

As always, visit chromestatus.com/features for a complete overview of Chrome’s developer features, and circle +Google Chrome Developers for more frequent updates.

Posted by Aurimas Lutikas, Software Engineer

It seems like yesterday that Chrome was first introduced on mobile devices to users running Android 4.0 Ice Cream Sandwich (ICS). Since then, twenty-four new Chrome releases and three new Android versions (Jellybean, Kitkat and Lollipop) have shipped. We’ve worked hard to make sure each version was faster, simpler and more secure than the last.

In the last year, we’ve seen the number of Chrome users running ICS drop by thirty percent. Developing new features on older phones has become increasingly challenging, and supporting ICS takes time away from building new experiences on the devices owned by the vast majority of our users. So, with Chrome’s 42nd release, we’ll stop updating Chrome on ICS devices. After Chrome 42, users on ICS devices can continue to use Chrome but won’t get further updates.

We’re excited to sharpen our focus on moving the web forward. If you’re interested in learning more about this change, please see the FAQ's.