Use italic and weight from font file if not specified

If the weight or italic values for a font are left unspecified when
creating a font in FontFamily_Delegate, use the values coming from the
font file itself, as the platform does.

Bug: 120548769
Test: N/A
Change-Id: Iade7da3c0e7aec26511848c6f78e9fad336f6915
(cherry picked from commit 47157742f860ada0b671986929423fdcfd215ca6)