polymer event_controller test fails on Dartium

[DartBot]

<img src="https://avatars.githubusercontent.com/u/4905639?v=3" align="left" width="96" height="96"hspace="10"> Issue by whesse
Originally opened as dart-lang/sdk#21012

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Since the roll to Chrome 38, the test pkg/polymer/test/event_controller_test has been failing on Dartium.
It is consistent on Windows and Mac, and flaky on linux.

This may be related to issue dart-lang/sdk#18931, which is a similar failure on many polymer tests.

But this showed up only with the Chrome roll. There may also be failures on the other polymer tests due to the roll, that are not showing because of the suppressions for issue dart-lang/sdk#18931.

Marking as flaky in the status file.

[jakemac53]

this test no longer exists