[chromedriver] Pass --test-type=webdriver when launching Chrome

[chromedriver] Pass --test-type=webdriver when launching Chrome.

This prevents Chrome from creating an infobar warning about unsupported flags (in particular --ignore-certificate-errors, which we also pass when launching Chrome).

BUG=chromedriver:799
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=275296

[stgao, 2014-06-04 06:09:56]

lgtm

[samuong, 2014-06-04 15:29:46]

The CQ bit was checked by samuong@chromium.org

[commit-bot: I haz the power, 2014-06-04 15:31:52]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/samuong@chromium.org/313003005/1

[commit-bot: I haz the power, 2014-06-04 21:34:53]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_chromium_gn_compile_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_chromium_gn_c...)

[commit-bot: I haz the power, 2014-06-04 21:39:58]

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

[commit-bot: I haz the power, 2014-06-04 21:39:58]

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

[samuong, 2014-06-05 00:50:31]

The CQ bit was checked by samuong@chromium.org

[commit-bot: I haz the power, 2014-06-05 00:51:41]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/samuong@chromium.org/313003005/1

[commit-bot: I haz the power, 2014-06-05 02:37:04]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_chromium_gn_compile_rel on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_chromium_gn_c...)

[commit-bot: I haz the power, 2014-06-05 02:44:45]

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

[commit-bot: I haz the power, 2014-06-05 02:44:45]

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

[samuong, 2014-06-06 01:17:57]

The CQ bit was checked by samuong@chromium.org

[commit-bot: I haz the power, 2014-06-06 01:20:53]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/samuong@chromium.org/313003005/1

[commit-bot: I haz the power, 2014-06-06 01:42:10]

Change committed as 275296