Update experiment test to only verify /exptest/... are bypassed

Update experiment test to only verify /exptest/... are bypassed

The exp_directive test verifies the experiment flag is passed to the
page, by bypassing any request to http://aws1.mdw.la/exptest/... when
the flag --data-reduction-proxy-experiment=test is set.  Which works
as expected.

However the favicon request from http://aws1.mdw.la/favicon.ico won't
be bypassed, causing the test to fail.  To fix the test, I'm adding an
optional url_pattern parameter to the bypass verification, that will
verify only /exptest/ urls are checked.

BUG=488232
Committed: https://crrev.com/d8c12436be2a7c39607fd078383f2519b0a4ac4b
Cr-Commit-Position: refs/heads/master@{#330644}

[bustamante, 2015-05-19 22:11:42]

bustamante@chromium.org changed reviewers:
+ sclittle@chromium.org

[bustamante, 2015-05-19 22:12:19]

bustamante@chromium.org changed reviewers:
+ bustamante@chromium.org

[bustamante, 2015-05-19 22:12:19]

PTAL when you get a chance, this should fix the majority of the waterfall
failures we're seeing.

[sclittle, 2015-05-19 22:17:45]

LGTM modulo nit

https://codereview.chromium.org/1141923004/diff/1/tools/chrome_proxy/integrat...
File tools/chrome_proxy/integration_tests/chrome_proxy_metrics.py (right):

https://codereview.chromium.org/1141923004/diff/1/tools/chrome_proxy/integrat...
tools/chrome_proxy/integration_tests/chrome_proxy_metrics.py:269: # Only check
the url's that contain the specified pattern
nit: add period at end of comment

[bustamante, 2015-05-19 22:26:09]

Thanks!

https://codereview.chromium.org/1141923004/diff/1/tools/chrome_proxy/integrat...
File tools/chrome_proxy/integration_tests/chrome_proxy_metrics.py (right):

https://codereview.chromium.org/1141923004/diff/1/tools/chrome_proxy/integrat...
tools/chrome_proxy/integration_tests/chrome_proxy_metrics.py:269: # Only check
the url's that contain the specified pattern
On 2015/05/19 22:17:45, sclittle wrote:
> nit: add period at end of comment

Done.

[bustamante, 2015-05-19 22:26:28]

The CQ bit was checked by bustamante@chromium.org

[bustamante, 2015-05-19 22:26:28]

The patchset sent to the CQ was uploaded after l-g-t-m from
sclittle@chromium.org
Link to the patchset: https://codereview.chromium.org/1141923004/#ps20001
(title: "Fix punctuation in comment")

[commit-bot: I haz the power, 2015-05-19 22:26:55]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1141923004/20001

[commit-bot: I haz the power, 2015-05-19 22:39:50]

Committed patchset #2 (id:20001)

[commit-bot: I haz the power, 2015-05-19 22:41:01]

Patchset 2 (id:??) landed as
https://crrev.com/d8c12436be2a7c39607fd078383f2519b0a4ac4b
Cr-Commit-Position: refs/heads/master@{#330644}