In the largest third-party win yet for the year-old Google Gears, as well as a win for the browser-as-a-platform, they say, News Corp’s MySpace social networking site has used the Google widgetry to upgrade its mail so users can search and sort their mail in real-time.

The MySpace news was barely out of the bag when Opera up and announced that it’ll be supporting Gears in its desktop and mobile browsers to push the browser as a full platform for applications, it said.

It said Gears will be in Opera Mobile 9.5 (now in beta) to be used along with Opera Dragonfly tools (now at the alpha stage) for developing and debugging applications for any connected environment.

Meanwhile MySpace explained that 170 million e-mail messages a day are sent from MySpace mail and its users, poor dears, have had to click through page after page to find a specific message until now.

Now – if they download the feature – or already have the open source Gears plug-in installed – they can use a message-related keyword and find the blasted thing – or sort by the mail headers date, from, status (unread), subject.

According to Google, it’s the Gears Database API with full test search that works the seemingly common Outlook-style magic and moves the mail off the server and onto the user’s machine.

For its part MySpace, which claims 110 million users, will be saving server-side resources. It didn’t say what it’s paying Google. Google of course enjoys a three-year $900 million deal supplying ads to MySpace.

Google Gears, by the way, is now simply Gears so it doesn’t seem like “just a Google thing,” Google said, expecting to support Firefox 3 and Safari too.