If U+FE0E is appended to the emoji code point, the glyph should have a
text presentation.
On the other hand, if U+FE0F is appended to the emoji code point, the
glyph should have an emoji presentation.

Bug: 11256006
Change-Id: I5187d44500b13a138e7ffbcf2c72e2da06374c8c

This issue was introduced by I22ce0e9eadc941f84e3a9b23462f194e51dd7180.
Need to decrement the two utf16 chars in KEYCAP handling.

To add unit tests, this CL also addresses the Bug: 24184208 by
introducing self built fonts since there is no good example in system
installed fonts.

Bug: 24184208
Change-Id: I23fa008adbaced78a3cb96442a6bc8892ab84ce8