Take mutex when calling into FreeType.

Take mutex when calling into FreeType.

SkScalerContext_FreeType::generateCharToGlyph and generateGlyphToChar
do not take a mutex when calling into FreeType, but they need to.
The setupSize method also requires the mutex to be locked, which is
not a problem since it currently always is, but add a debug assert
to ensure that it continues to be.

BUG=chromium:542640
Committed: https://skia.googlesource.com/skia/+/3f846ae913f0e01eedf889fff062e9a1dc9f4f8b

[bungeman-skia, 2015-11-03 18:50:06]

The CQ bit was checked by bungeman@google.com to run a CQ dry run

[commit-bot: I haz the power, 2015-11-03 18:50:09]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1431683006/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1431683006/1

[bungeman-skia, 2015-11-03 18:54:31]

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

[mtklein, 2015-11-03 19:03:40]

lgtm

[commit-bot: I haz the power, 2015-11-03 19:03:57]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-11-03 19:03:58]

Dry run: This issue passed the CQ dry run.

[bungeman-skia, 2015-11-03 19:06:40]

The CQ bit was checked by bungeman@google.com

[commit-bot: I haz the power, 2015-11-03 19:06:47]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1431683006/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1431683006/1

[commit-bot: I haz the power, 2015-11-03 19:07:23]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/3f846ae913f0e01eedf889fff062e9a1dc9f4f8b

[herb_g, 2015-11-03 19:09:28]

lgtm

https://codereview.chromium.org/1431683006/diff/1/src/ports/SkFontHost_FreeTy...
File src/ports/SkFontHost_FreeType.cpp (right):

https://codereview.chromium.org/1431683006/diff/1/src/ports/SkFontHost_FreeTy...
src/ports/SkFontHost_FreeType.cpp:951: FT_Error
SkScalerContext_FreeType::setupSize() {
Maybe change the name to indicate that this routine assumes a held lock.
setupSizeLocked?