Gmail for iOS app updated and the update brings a feature that opens Gmail links in Google Apps including Chrome, YouTube and Google Maps, provided you have these apps installed in your iDevice. Earlier whenever you click on links in Gmail they will open in browser and now the links will go to the Google apps, this helps Google in keeping users in the Google app world.
If you don’t want to open links like this and prefers the default way of opening links in Gmail browser you can revert to that using in app settings. To do this, go to settings icon next to the the account switcher, uncheck the apps you don’t want to use the new feature. The links when open in Chrome add a Gmail button, clicking on that will take you back to Gmail.
Another feature that is added in this update is better multiple account management, if you have multiple accounts you can now sign-out of a single account instead of signing-out from all accounts. This is a very useful feature for power users who use multiple accounts.