Google knows how to promote its products and that is what it has been doing with the past products. This tie it is promoting Google Play by featuring it in Google Bar.
Google Play which also knows to be Android Market until recently, is the one stop shop for applications, music, movie and books. Weather a user is on a mobile device or a desktop computer, Google Play satisfy the customer in both ways.
Earlier Google placed G+ on the bar to boost its usage.
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