Disable still-flaky test TaskManagerBrowserTest.WebWorkerJSHeapMemory.

Disable still-flaky test TaskManagerBrowserTest.WebWorkerJSHeapMemory.

This test is inherently flaky because it relies on a preset timeout
period. It needs to be rewritten to use something that works like
task_manager::browsertest_util::WaitForTaskManagerRows, i.e.,
by waiting for taskmanager changes until the condition is satisfied.

TBR=thakis@chromium.org
BUG=259368
Committed: https://crrev.com/c0c89fde409f090d0097a385611eff711b22577e
Cr-Commit-Position: refs/heads/master@{#322862}

[ncarter (slow), 2015-03-30 19:55:05]

nick@chromium.org changed reviewers:
+ thakis@chromium.org

[ncarter (slow), 2015-03-30 19:55:12]

The CQ bit was checked by nick@chromium.org

[commit-bot: I haz the power, 2015-03-30 19:56:07]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1045943002/1

[commit-bot: I haz the power, 2015-03-30 20:55:31]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-03-30 20:56:22]

Patchset 1 (id:??) landed as
https://crrev.com/c0c89fde409f090d0097a385611eff711b22577e
Cr-Commit-Position: refs/heads/master@{#322862}