Temporarily disable InputManagerTest.PowerButton

BUG=424109
TBR=mukai@chromium.org

Review URL: https://codereview.chromium.org/660773002

Cr-Commit-Position: refs/heads/master@{#299875}

athena/input/input_manager_unittest.cc

@@ -72,7 +72,9 @@ class ScopedPowerButtonTimeoutShortener {
 
 typedef test::AthenaTestBase InputManagerTest;
 
-TEST_F(InputManagerTest, PowerButton) {
+// This fails on bots. crbug.com/424109.
+// Investigate once crbug.com/424093 is fixed.
+TEST_F(InputManagerTest, DISABLED_PowerButton) {
   test::ScopedPowerButtonTimeoutShortener shortener;
   TestPowerButtonObserver observer;