Remove unnecessary includes of GlyphBuffer.h.

Previously this was included in many other source files.
For me, this reduces the number of affected build targets from 889 to 93.

Review URL: https://codereview.chromium.org/344873002

git-svn-id: svn://svn.chromium.org/blink/trunk@176521 bbb929c8-8fbe-4397-9dbb-9b2b20218538