Adapting web games
Web games look and work great on ChromeOS. You can reach more users and provide a nicer integration by packing your app as a PWA. Read up on PWAs with the following links:
Touchscreens
Many ChromeOS devices have touch screens. While most touch-based input should work with no additional work for web games, you should be careful you are not using input methods that are specific to mouse input, eg. if you are watching for events like mousedown and touchmove.
Some further information and best practices can be found here and here.
Stylus support
Many ChromeOS devices come with a stylus or can operate with an external bluetooth drawing tablet like the Wacom Intuos. Drawing apps and swipe-based games can reach large numbers of users on the web, and ChromeOS is the perfect platform to play them on. In addition to the experience you would get on other platforms, ChromeOS can take advantage of a special low-latency hint that can provide super fast screen response. Check out this article for more information.
Game controllers
Some users will want to interact with your game using a game controller. This can make your game really stand out and increase user engagement. For more information check out the Gamepad API.
Buttons are mapped to common values following a common mapping. Unfortunately, not all game controller manufacturers follow the same mapping conventions. Allowing your users to select from different popular controller mappings will ensure the best experience.
Game engines
Many game engines have web targets that simplify tricky inputs and complicated browser support issues, which can help you focus on building a great game for your users.
Some engines you may wish to check out are Construct, Defold, Phaser, Pixi, Unity, and Cocos2d-x.