Just what I needed and even more.

You just select a text on a page, then use either a context menu or a keyboard shortcut and voilà - you are redirected to the Google Translate page with the selected text prefilled into the related box.

In addition to that you can also use the "Text to Speech" option to hear the pronunciation, and also an option to translate the whole page at once.

So simple concept, yet so convenient.
Thank you!