Revert of SkTime::GetNSecs() (patchset #10 id:180001 of https://codereview.chromium.org/1422513003/ )

Reason for revert:
https://codereview.chromium.org/1412453006

Original issue's description:
> SkTime::GetNSecs()
>
>    - Move high-precision wall timers from tools/timer to SkTime.
>    - Implement SkTime::GetMSecs() in terms of SkTime::GetNSecs().
>    - Delete unused tools/timer code.
>
> I have no idea what's going on there in src/animator.
> I don't intend to investigate.
>
> BUG=skia:
>
> Committed: https://skia.googlesource.com/skia/+/70084cbc16ee8162649f2601377feb6e49de0217
>
> CQ_EXTRA_TRYBOTS=client.skia.compile:Build-Ubuntu-GCC-x86_64-Debug-CrOS_Link-Trybot
>
> Committed: https://skia.googlesource.com/skia/+/a1840d50e29fd95e4df2d1168fe54c34c2a5c30c

TBR=caryclark@google.com,reed@google.com,mtklein@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=skia:

Review URL: https://codereview.chromium.org/1417753003
19 files changed