Update BUILD.public a bit.

 - SSE2 files are unfortunately now mixed-case, _SSE2 or _sse2.
 - Adds lists for SSSE3 and SSE4 files.
 - Remove SkDocument_PDF_None.cpp
 - Remove a few more references to animator.
 - Exclude private headers from HDRS.
 - Formatting and notes.

BUG=skia:

Review URL: https://codereview.chromium.org/1298003007
2 files changed