Add GetDebugState() in SendAlgorithmInterface().

Add GetDebugState() in SendAlgorithmInterface().

Merge internal change: 129053230

R=rch@chromium.org
BUG=

[danzh1, 2016-08-08 18:52:54]

The CQ bit was checked by danzh@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-08-08 18:53:27]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-08-08 19:10:05]

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

[commit-bot: I haz the power, 2016-08-08 19:10:06]

Dry run: Try jobs failed on following builders:
  chromeos_x86-generic_chromium_compile_only_ng on
master.tryserver.chromium.linux (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.linux/builders/chromeos_x86-ge...)

[Ryan Hamilton, 2016-08-09 16:32:00]

Please trip the CL description to remove references to internal projects that
are not really pat of the chromium CL.

[danzh1, 2016-08-09 19:38:25]

Description was changed from

==========
Allow Debugging information to be added to Tracegraf via flag

This cl adds an optional debug_state field to TracegrafPackets, which
can be populated by arbitrary debugging strings.

This field will not be populated by default.  It will only be
populated when a developer manually flips the
gfe2_quic_tracegraf_debugging_state_enabled flag to true on a given
GFE.  Even then, the field will only be populated if the underlying
congestion-control algorithm's GetDebugState function returns a
non-empty string

Why is this useful?  This field is intended for debugging experimental
congestion-control algorithms (such as PCC) while they are still under
development.  It's tantamount to being able to add printfs to each
packet event while debugging the algorithm.  In such a case, its handy
to track the state of the algorithm along with each packet event.
Adding custom fields to TracegrafConnection for that purpose is
overkill.

LOG_STORAGE_INCREASE(GB/week): 0 GB / week
This field will only be populated during occasional debugging and WILL
ONLY BE OUTPUT TO A LOCAL LOGFILE.  I have added test cases that ensure
that this field is cleared before it is sent to logs storage as well as
the appropriate annotations in the log file.

Merge internal change: 129053230

R=rch@chromium.org
BUG=
==========

to

==========
Add GetDebugState() in SendAlgorithmInterface().

Merge internal change: 129053230

R=rch@chromium.org
BUG=
==========

[danzh1, 2016-08-09 19:38:46]

On 2016/08/09 16:32:00, Ryan Hamilton wrote:
> Please trip the CL description to remove references to internal projects that
> are not really pat of the chromium CL.

done.

[Ryan Hamilton, 2016-08-09 21:57:13]

lgtm