Chrome proxy telemetry test: better via header checking

Ignore cache hits and invalid responses.
Also log bypass during via header checking and restart browser for each page.

BUG=374413
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=271498

[bolian, 2014-05-16 22:16:35]

Hi Ben,

This is a fix to improve current via header validation.

Thanks,
Bolian

[bengr, 2014-05-17 06:00:52]

On 2014/05/16 22:16:35, bolian wrote:
> Hi Ben,
> 
> This is a fix to improve current via header validation.
> 
> Thanks,
> Bolian

lgtm, but please fix the description before submitting.

[bolian, 2014-05-19 16:53:02]

On 2014/05/17 06:00:52, bengr1 wrote:
> On 2014/05/16 22:16:35, bolian wrote:
> > Hi Ben,
> > 
> > This is a fix to improve current via header validation.
> > 
> > Thanks,
> > Bolian
> 
> lgtm, but please fix the description before submitting.

Done. Thanks.

[bolian, 2014-05-19 17:09:01]

The CQ bit was checked by bolian@chromium.org

[commit-bot: I haz the power, 2014-05-19 17:09:59]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/bolian@chromium.org/292453006/60001

[commit-bot: I haz the power, 2014-05-19 20:42:19]

FYI, CQ is re-trying this CL (attempt #1).
Please consider checking whether the failures are real,
and report flakes to chrome-troopers@google.com.
The failing builders are:
  linux_chromium_chromeos_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/linux_chromium_chrome...)

[commit-bot: I haz the power, 2014-05-19 21:58:36]

Change committed as 271498