HTMLEntityTable could use char to reduce binary size

Merging from webkit CL http://trac.webkit.org/changeset/155559

Using LChar instead of UChar in HTMLEntityTable reduces the
binary size by around 18Kb.

Review URL: https://codereview.chromium.org/120393003

git-svn-id: svn://svn.chromium.org/blink/trunk@164437 bbb929c8-8fbe-4397-9dbb-9b2b20218538