The celebrated openness of the Internet -- network providers are not supposed to give preferential treatment to any traffic -- is quietly losing powerful defenders. Google Inc. has approached major cable and phone companies that carry Internet traffic with a proposal to create a fast lane for its own content, according to documents reviewed by The Wall Street Journal. Google has traditionally been one of the loudest advocates of equal network access for all content providers. At risk is a principle known as network neutrality: Cable and phone companies that operate the data pipelines are supposed to treat all traffic...