Fix cluster-fuzz crash with internal EventSender API.

Fix cluster-fuzz crash with internal EventSender API.

In release mode a DCHECK was compiled out and caused a crash; it was
correctly asserting in the Debug builds. Change the DCHECK into a
runtime check that throws an exception. This addresses the cluster fuzz
crash.

BUG=472058
TEST=out/Release/content_shell --dump-render-tree --use-gl=any --disable-gl-drawing-for-test file:///work/issues/472058/test.html

Committed: https://crrev.com/bd2a165a1018ec23d060b72b29af7fe26e5f1828
Cr-Commit-Position: refs/heads/master@{#330659}

[dtapuska, 2015-05-19 14:56:50]

dtapuska@chromium.org changed reviewers:
+ rbyers@chromium.org

[Rick Byers, 2015-05-19 22:39:54]

What does your TEST= line refer to, just some local file you were using for
testing?  I think TEST= is intended to be used to list the automated test that
covers the case, so TEST=None is fine here (although in practice we don't
consistently use TEST= anymore - I don't bother unless it's non-obvious).

Anyway LGTM

[dtapuska, 2015-05-19 22:51:04]

On 2015/05/19 22:39:54, Rick Byers wrote:
> What does your TEST= line refer to, just some local file you were using for
> testing?  I think TEST= is intended to be used to list the automated test that
> covers the case, so TEST=None is fine here (although in practice we don't
> consistently use TEST= anymore - I don't bother unless it's non-obvious).
> 
> Anyway LGTM

I wrote it in there because the args to content_shell caused me to reproduce the
issue. When I ran content_shell without any args it didn't fail. So I went back
to the clusterfuzz issue and copied the args.. The test.html is essentially in
the bug so I thought that was obvious.

[dtapuska, 2015-05-19 22:51:20]

The CQ bit was checked by dtapuska@chromium.org

[commit-bot: I haz the power, 2015-05-19 22:53:04]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1140813007/1

[commit-bot: I haz the power, 2015-05-20 00:30:22]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-05-20 00:31:19]

Patchset 1 (id:??) landed as
https://crrev.com/bd2a165a1018ec23d060b72b29af7fe26e5f1828
Cr-Commit-Position: refs/heads/master@{#330659}