fix some bit-rot in the ios port of sampleapp

BUG=skia:

Review URL: https://codereview.chromium.org/637263004
Add SkTypeface::getBounds()

mirrored from https://codereview.chromium.org/666303002/

BUG=skia:
TBR=

Review URL: https://codereview.chromium.org/676523002