TBA13: system/widget font tests: font-family not returned in getComputedStyle

getComputedStyle(el).getPropertyValue("font-family") is (mostly) missing in Android TB13

system fonts test

for example, I get all 17 items tested as

• windows: "12px normal 400 sans-serif"
• linux: "15px normal 400 sans-serif"
• android: "16px normal 400 " (note the trailing space, because I didn't expect to have to parse for empty strings :))

widget fonts test

for example

windows:

	"monospace 13.3333px": ["datetime", "datetime-local", "time"],
	"monospace 13px": ["textarea"],
	"sans-serif 13.3333px": [19 items],
	"sans-serif 13px": ["image"]

linux:

	"monospace 12px": ["textarea"],
	"monospace 13.3333px": ["datetime", "datetime-local", "time"],
	"sans-serif 13.3333px": [19 items],
	"sans-serif 13px": ["image"]

android should be same as linux, but the 19 items is missing the font-family property: note the leading space

	" 13.3333px": [19 items],
	"monospace 12px": ["textarea"],
	"monospace 13.3333px": ["datetime", "datetime-local", "time"],
	"sans-serif 13px": ["image"]

cc @pierov