Use 'std::equal' in VectorComparer

Use 'std::equal' instead of a home-brewed cycle in the
'non-memcmp' version of the VectorComparer class, making
the code simpler.

Review URL: https://codereview.chromium.org/238833003

git-svn-id: svn://svn.chromium.org/blink/trunk@171579 bbb929c8-8fbe-4397-9dbb-9b2b20218538