A view of the Exxon Mobil refinery in Baytown, TexasBy Anna Driver HOUSTON (Reuters) – Shareholders of the top two U.S. oil companies on Wednesday rejected proposals to add directors with climate change expertise to their boards, but a measure passed at one, Chevron Corp, could give new power to minority investors with environmental concerns. Proposals to add an independent director with expertise in climate change received the support of about 20 percent of shareholders at each company, according to preliminary tallies provided at Chevron’s annual meeting and that of Exxon Mobil Corp. By contrast, an advisory proposal allowing Chevron shareholders with stakes of at least 3 percent to nominate independent directors passed.