Rename SkFontHost_none.cpp to SkFontMgr_empty_factory.

Rename SkFontHost_none.cpp to SkFontMgr_empty_factory.

When the current function was added in
https://skia.googlesource.com/skia/+/070da5edcb1c6e9b9507f06a5e2c270e1c1fd796%5E%21/#F3
the SkFontHost was still alive and well. Now that this file no
longer contains any SkFontHost related code, rename the file for
clarity and uniformity.

Committed: https://skia.googlesource.com/skia/+/bd1fb49dd96d130aba5b2c17190b93b638469e86

[bungeman-skia, 2015-06-22 22:32:47]

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

[commit-bot: I haz the power, 2015-06-22 22:33:00]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1196313003/1

[bungeman-skia, 2015-06-22 22:33:24]

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

[bungeman-skia, 2015-06-22 22:33:24]

One more cleanup along the way to a better named set of font related files.

[commit-bot: I haz the power, 2015-06-22 22:38:18]

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

[commit-bot: I haz the power, 2015-06-22 22:38:19]

Dry run: This issue passed the CQ dry run.

[reed1, 2015-06-22 23:00:45]

lgtm

[bungeman-skia, 2015-06-23 14:17:28]

The CQ bit was checked by bungeman@google.com

[commit-bot: I haz the power, 2015-06-23 14:17:41]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1196313003/1

[commit-bot: I haz the power, 2015-06-23 14:18:27]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/bd1fb49dd96d130aba5b2c17190b93b638469e86