Revert 40099 - Revert 39998 Revert 39996 Refine IPv6 probe to require that ...

Revert 40099 - Revert 39998  Revert 39996  Refine IPv6 probe to require that the client has an IPv6 address on an interface

It is indeed causing a perf regression in startup on Linux...
I'll need to rearchitect to do the probes asynchronously, and get
off the startup-critical-path.

This currently only works on Posix, not windows.

Network changes are monitored, and the test is repeated each time interfaces
change (which is a subset of any IP addresses changing).

The test performed is still relatively low latency, and we *may* need
to eventually move to an high latency test, such as a DNS resolution,
or an actual test connection.  If we move in that direction, then we'll
need to post a task to perform the work, rather than immediately returning.

BUG=25680
BUG=12754
r=wtc,eroman
Review URL: http://codereview.chromium.org/652072

TBR=jar@chromium.org
Review URL: http://codereview.chromium.org/660073

TBR=jar@chromium.org
Review URL: http://codereview.chromium.org/661164

TBR=jar@chromium.org

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=40101