Two years ago — an epoch in Silicon Valley time — AOL chief executive Tim Armstrong proposed a merger to Yahoo chief executive Marissa Mayer. Both Armstrong and Mayer were ex-Googlers hired to run and rescue these formerly marquee internet destinations. But AOL and Yahoo were struggling in increasingly mobile online world dominated by Google and Facebook. Mayer rejected Armstrong’s offer. But now that AOL-Yahoo merger could take place in a wholly unexpected manner — thanks to Verizon, the largest U.S.