Mojo: Make GetDefault{AsyncWaiter,Logger} static methods of Environment.

Mojo: Make GetDefault{AsyncWaiter,Logger} static methods of Environment.

Also:
* Move SetMinimumLogLevel() into MojoLogger itself. (This is somewhat
  unfortunate, since may not be thread-safe -- in particular, when
  sharing a copy of base's logging as in a component=shared_library
  build, it becomes blatantly unsafe. Thus it's of slightly dubious
  value. But it's where it belongs logically. Of course, sharing a log
  level across applications that are cohabiting a process is dubious.
  Avoiding this would mean at least layering a log level on top of
  Chromium's.)
* Allow the (standalone) Environment's choices for default AsyncWaiter
  and/or Logger to be overridden.

R=darin@chromium.org

Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=278401

[viettrungluu, 2014-06-19 06:48:27]

Friendly ping.

[darin (slow to review), 2014-06-19 06:59:31]

LGTM

[viettrungluu, 2014-06-19 07:09:48]

The CQ bit was checked by viettrungluu@chromium.org

[commit-bot: I haz the power, 2014-06-19 07:11:05]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/viettrungluu@chromium.org/339403003/1

[commit-bot: I haz the power, 2014-06-19 11:39:16]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-06-19 11:39:18]

Try jobs failed on following builders:
  chromium_presubmit on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/chromium_presubmit/bu...)

[viettrungluu, 2014-06-19 16:29:35]

Committed patchset #1 manually as r278401.