Fix logic in PerfProfiler.is_supported.

Fix logic in PerfProfiler.is_supported.

The current logic doesn't work when we run the test locally on the DUT because the browser_type is 'system'.

BUG=411280
TEST=testPerfProfiler skipped on the DUT.

Committed: https://crrev.com/111ceb9e054cef9c71c37073c8b6d3858fc4cd4b
Cr-Commit-Position: refs/heads/master@{#293833}

[achuithb, 2014-09-08 13:55:51]

achuith@chromium.org changed reviewers:
+ tbarzic@chromium.org

[achuithb, 2014-09-08 13:55:51]

Please review Toni

[tbarzic, 2014-09-08 17:14:27]

On 2014/09/08 13:55:51, achuithb wrote:
> Please review Toni

lgtm

[achuithb, 2014-09-08 19:22:21]

The CQ bit was checked by achuith@chromium.org

[commit-bot: I haz the power, 2014-09-08 19:23:46]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/achuith@chromium.org/554613003/1

[commit-bot: I haz the power, 2014-09-08 23:45:19]

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

[commit-bot: I haz the power, 2014-09-08 23:45:20]

Exceeded time limit waiting for builds to trigger.

[achuithb, 2014-09-08 23:47:14]

The CQ bit was checked by achuith@chromium.org

[commit-bot: I haz the power, 2014-09-08 23:50:49]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/achuith@chromium.org/554613003/1

[commit-bot: I haz the power, 2014-09-09 01:48:10]

Committed patchset #1 (id:1) as e1a1e9ea2e43d1e37cc6bb863deabc5b09346f07

[commit-bot: I haz the power, 2014-09-10 03:49:42]

Patchset 1 (id:??) landed as
https://crrev.com/111ceb9e054cef9c71c37073c8b6d3858fc4cd4b
Cr-Commit-Position: refs/heads/master@{#293833}