Overdue reorg of source tree to support multiple platforms & devices.

Bug: skia:
Change-Id: I1248a529a932ed5ef32952a1bb7eca56ee1c5f25
Reviewed-on: https://skia-review.googlesource.com/136170
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
57 files changed