Work around CG assert drawing tiny glyphs.

Work around CG assert drawing tiny glyphs.

For some fonts when drawing glyphs at CGFLOAT_MIN size,
CG will assert internally. Instead, request such glyphs at size 1,
and scale them down to 0 with a transform.

This change follows the pattern set by
3490263287e9432119c501884e45840de4d986bc
"Replace use of deprecated CG methods." on master.

BUG=chromium:441538
R=reed@google.com

Committed: https://skia.googlesource.com/skia/+/f4153260844a88d208c30bac5cc6902e716289c9

[bungeman-skia, 2014-12-12 19:54:32]

bungeman@google.com changed reviewers:
+ mtklein@google.com, reed@google.com

[bungeman-skia, 2014-12-12 19:54:32]

This is a change directly to the m40 branch. The master code has changed to both
fix this already, and also has changed a whole lot, so there is not way to try
this out on master. On the other hand, this essentially does what master is
currently doing for this specific case.

[reed1, 2014-12-12 19:56:19]

lgtm

[bungeman-skia, 2014-12-12 19:59:56]

Committed patchset #1 (id:1) manually as
f4153260844a88d208c30bac5cc6902e716289c9 (presubmit successful).