Revert of SkTime::GetNSecs()

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:

Committed: https://skia.googlesource.com/skia/+/5a06df46864f010befaf8c57af1801fb43cbea86

[mtklein, 2015-10-23 00:48:54]

Created Revert of SkTime::GetNSecs()

[commit-bot: I haz the power, 2015-10-23 00:49:12]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1417753003/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1417753003/1

[commit-bot: I haz the power, 2015-10-23 00:49:26]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/5a06df46864f010befaf8c57af1801fb43cbea86