Centralize bitmap glyph positioning

Centralize all text drawing for bitmap devices into SkGlyphRunListDrawer.
All drawing decisions are encapsulated in this class, and its behavior
only depends on contant properties of the device.

The method drawForBitmap will probably have to be converted to a template
based in preliminary performance numbers.

Change-Id: Id21567c1511eee9d2e9e20c7ae93544530cfdb81
Reviewed-on: https://skia-review.googlesource.com/143106
Reviewed-by: Mike Klein <mtklein@google.com>
Reviewed-by: Herb Derby <herb@google.com>
Commit-Queue: Herb Derby <herb@google.com>
7 files changed