Telemetry: Add more details to inspector_backend exceptions.

Telemetry: Add more details to inspector_backend exceptions.

Previously, inspector_backend would always throw a
DevtoolsTargetCrashException. Now, it throws either a
DevtoolsTargetCrashException or a TimeoutException. The CL also adds the
debugger_url to the exception as further debugging information.

There were exactly 2 files that tried to catch a DevtoolsTargetCrashException.
I changed fast_navigation_profile_extender to catch Error instead. I will be
improving this class in the future to have better exception handling.
chrome_proxy_measurements caught a DevtoolsTargetCrashException, but its
behavior is better suited by catching a TimeoutException.

BUG=460625
Committed: https://crrev.com/910d6e733bac30f15f76054eb101a81987f8c675
Cr-Commit-Position: refs/heads/master@{#319193}

[erikchen, 2015-02-28 00:26:38]

erikchen@chromium.org changed reviewers:
+ nednguyen@google.com

[erikchen, 2015-02-28 00:26:39]

nednguyen: Please review.

[nednguyen, 2015-03-04 00:18:17]

nednguyen@google.com changed reviewers:
+ dtu@chromium.org, sullivan@chromium.org

[sullivan, 2015-03-04 14:56:30]

lgtm

[erikchen, 2015-03-04 22:14:33]

The CQ bit was checked by erikchen@chromium.org

[commit-bot: I haz the power, 2015-03-04 22:15:37]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/959423003/20001

[commit-bot: I haz the power, 2015-03-04 22:19:37]

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

[commit-bot: I haz the power, 2015-03-04 22:19:37]

Try jobs failed on following builders:
  ios_rel_device_ninja on tryserver.chromium.mac (JOB_FAILED,
http://build.chromium.org/p/tryserver.chromium.mac/builders/ios_rel_device_ni...)

[erikchen, 2015-03-05 00:13:24]

The CQ bit was checked by erikchen@chromium.org

[erikchen, 2015-03-05 00:13:24]

The patchset sent to the CQ was uploaded after l-g-t-m from
sullivan@chromium.org
Link to the patchset: https://codereview.chromium.org/959423003/#ps40001 (title:
"Rebase against top of tree.")

[commit-bot: I haz the power, 2015-03-05 00:14:23]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/959423003/40001

[commit-bot: I haz the power, 2015-03-05 02:08:01]

Committed patchset #3 (id:40001)

[commit-bot: I haz the power, 2015-03-05 02:09:00]

Patchset 3 (id:??) landed as
https://crrev.com/910d6e733bac30f15f76054eb101a81987f8c675
Cr-Commit-Position: refs/heads/master@{#319193}