cairo's configure.ac turns on support for pixman's glyph cache if 0.27.1 or newer is available. if pkg-config --exists 'pixman-1 >= 0.27.1'; then AC_DEFINE([HAS_PIXMAN_GLYPHS], 1, [Enable pixman glyph cache]) fi 0.28.0 is stable. There's no reason not to depend on it.
Done with 1.12.12 version bump.