Use SkTypeface::getBounds() in bounding-box calculations.

Use SkTypeface::getBounds() in bounding-box calculations.

This should produce tighter conservative bounding boxes for text than the
approximation code it replaces.

Recording performance is neutral on my desktop.  Playback performance
improves by up to 15% on text heavy pages, e.g.

  desk_pokemonwiki.skp_1 3.24ms -> 2.83ms  0.87x
        desk_baidu.skp_1 1.91ms -> 1.58ms  0.83x

Committed: https://skia.googlesource.com/skia/+/bf8dc343df4fbdcb8af546eb68b640e011a33489

CQ_EXTRA_TRYBOTS=client.skia:Test-Win7-ShuttleA-HD2000-x86-Debug-Trybot

Review URL: https://codereview.chromium.org/680363003