Populate the name-to-pseudo map lazily

Sort pseudoTypeMap[] to allow using binary search to look up the name.

BUG=365613

Review URL: https://codereview.chromium.org/256563002

git-svn-id: svn://svn.chromium.org/blink/trunk@173317 bbb929c8-8fbe-4397-9dbb-9b2b20218538