Sprinkle some DVLOGs in media::WallClockTimeSource.

Sprinkle some DVLOGs in media::WallClockTimeSource.

Matches what we have in AudioRendererImpl, which is our only other
TimeSource implementation.

TBR=xhwang

Committed: https://crrev.com/b7b8f696220f6ae040d48ea4822cefcea295d6df
Cr-Commit-Position: refs/heads/master@{#294684}

[scherkus (not reviewing), 2014-09-12 21:08:58]

scherkus@chromium.org changed reviewers:
+ xhwang@chromium.org

[scherkus (not reviewing), 2014-09-12 21:09:05]

The CQ bit was checked by scherkus@chromium.org

[commit-bot: I haz the power, 2014-09-12 21:12:16]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patchset/551273004/1

[xhwang, 2014-09-12 21:23:22]

lgtm

[commit-bot: I haz the power, 2014-09-12 22:41:25]

Committed patchset #1 (id:1) as 1abb91889f0b0e14040efb087d1edfaaca7153b4

[commit-bot: I haz the power, 2014-09-12 22:44:47]

Patchset 1 (id:??) landed as
https://crrev.com/b7b8f696220f6ae040d48ea4822cefcea295d6df
Cr-Commit-Position: refs/heads/master@{#294684}