Add a useful error message for run-webkit-tests broken --target handling.

Add a useful error message for run-webkit-tests broken --target handling.

This will hopefully prevent some wasted time until the underlying
problem is fixed.

R=kbr@chromium.org, skobes@chromium.org
BUG=539509
Committed: https://crrev.com/afd25fb38db90dea1058240aceb6bbc02578f947
Cr-Commit-Position: refs/heads/master@{#376092}

[skobes, 2016-02-18 03:31:11]

lgtm

[Dirk Pranke, 2016-02-18 03:34:16]

The CQ bit was checked by dpranke@chromium.org

[commit-bot: I haz the power, 2016-02-18 03:35:06]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1708973002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1708973002/1

[commit-bot: I haz the power, 2016-02-18 04:26:50]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2016-02-18 04:28:18]

Description was changed from

==========
Add a useful error message for run-webkit-tests broken --target handling.

This will hopefully prevent some wasted time until the underlying
problem is fixed.

R=kbr@chromium.org, skobes@chromium.org
BUG=539509
==========

to

==========
Add a useful error message for run-webkit-tests broken --target handling.

This will hopefully prevent some wasted time until the underlying
problem is fixed.

R=kbr@chromium.org, skobes@chromium.org
BUG=539509

Committed: https://crrev.com/afd25fb38db90dea1058240aceb6bbc02578f947
Cr-Commit-Position: refs/heads/master@{#376092}
==========

[commit-bot: I haz the power, 2016-02-18 04:28:18]

Patchset 1 (id:??) landed as
https://crrev.com/afd25fb38db90dea1058240aceb6bbc02578f947
Cr-Commit-Position: refs/heads/master@{#376092}

[dstockwell, 2016-02-19 03:02:10]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1714773002/ by dstockwell@chromium.org.

The reason for reverting is: Broke workflows not using the "blessed" output
directories.

See: https://codereview.chromium.org/1705233003#msg6.

[alancutter (OOO until 2018), 2016-02-19 03:36:29]

On 2016/02/19 at 03:02:10, dstockwell wrote:
> A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1714773002/ by dstockwell@chromium.org.
> 
> The reason for reverting is: Broke workflows not using the "blessed" output
directories.
> 
> See: https://codereview.chromium.org/1705233003#msg6.

It would also break the "blessed" out/Default GN workflow.