Use base::StringPairs where appropriate from src/google_apis

Becuase base/strings/string_split.h defines:
typedef std::vector<std::pair<std::string, std::string> > StringPairs;

BUG=412250

Review URL: https://codereview.chromium.org/591413002

Cr-Commit-Position: refs/heads/master@{#296888}
1 file changed