Disable flaky HangWatcherSnapshotTest.HungThreadIDs

Despite some attempts to fix it, the test is still a bit flaky.

Bug: 1078828
Change-Id: I16d6f8efc7aaa8c042f1f15f5887d25ffc78ea62
Tbr: olivierli@google.com
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2357600Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798287}

base/threading/hang_watcher_unittest.cc

@@ -567,7 +567,8 @@ TEST_F(HangWatcherSnapshotTest, NonActionableReport) {
   }
 }
 
-TEST_F(HangWatcherSnapshotTest, HungThreadIDs) {
+// Disabled for being flaky. crbug.com/1078828
+TEST_F(HangWatcherSnapshotTest, DISABLED_HungThreadIDs) {
   // During hang capture the list of hung threads should be populated.
   hang_watcher_.SetOnHangClosureForTesting(base::BindLambdaForTesting([this]() {
     EXPECT_EQ(hang_watcher_.GrabWatchStateSnapshotForTesting()