Google Inc. plans to open showrooms in six U.S. cities, in order to promote its latest products to step up retail efforts against Apple Inc. and Microsoft Corp. for the holiday season. The showrooms are called Winter Wonderlabs, and they will feature products like the Nexus 7 tablets, Chromebook computers and Chromecast video streaming devices. Customers can order the products online after seeing them in the stores. Google has invested more resources to increase its position in hardware and joined forces with Intel Corp. this year to promote products.