Disable failing media unittests on chromeos.

telemetry/telemetry/internal/actions/loop_unittest.py

Index: telemetry/telemetry/internal/actions/loop_unittest.py
diff --git a/telemetry/telemetry/internal/actions/loop_unittest.py b/telemetry/telemetry/internal/actions/loop_unittest.py
index 6438cac54e5abc9e4872576b3c292fc38ebe1320..8928b864ddf7be08e5fdd801acc750a9302810c4 100644
--- a/telemetry/telemetry/internal/actions/loop_unittest.py
+++ b/telemetry/telemetry/internal/actions/loop_unittest.py
@@ -19,7 +19,8 @@ class LoopActionTest(tab_test_case.TabTestCase):
     tab_test_case.TabTestCase.setUp(self)
     self.Navigate('video_test.html')
 
-  @decorators.Disabled('android', 'linux')  # crbug.com/418577
+  # crbug.com/749890
+  @decorators.Disabled('android', 'linux', 'chromeos')
   def testLoopWithNoSelector(self):
     """Tests that with no selector Loop action loops first media element."""
     action = loop.LoopAction(loop_count=2, selector='#video_1',
@@ -30,7 +31,8 @@ class LoopActionTest(tab_test_case.TabTestCase):
     self.assertTrue(self._tab.EvaluateJavaScript(VIDEO_1_LOOP_CHECK))
     self.assertFalse(self._tab.EvaluateJavaScript(AUDIO_1_LOOP_CHECK))
 
-  @decorators.Disabled('android', 'linux')  # crbug.com/418577
+  # crbug.com/749890
+  @decorators.Disabled('android', 'linux', 'chromeos')
   def testLoopWithAllSelector(self):
     """Tests that Loop action loops all video elements with selector='all'."""
     action = loop.LoopAction(loop_count=2, selector='all',
@@ -44,7 +46,8 @@ class LoopActionTest(tab_test_case.TabTestCase):
     self.assertTrue(self._tab.EvaluateJavaScript(VIDEO_1_LOOP_CHECK))
     self.assertTrue(self._tab.EvaluateJavaScript(AUDIO_1_LOOP_CHECK))
 
-  @decorators.Disabled('android', 'linux')  # crbug.com/418577
+  # crbug.com/749890
+  @decorators.Disabled('android', 'linux', 'chromeos')
   def testLoopWaitForLoopTimeout(self):
     """Tests that wait_for_loop timeout_in_secondss if video does not loop."""
     action = loop.LoopAction(loop_count=2, selector='#video_1',