Disable the flaky NetworkQualityEstimator unittest on ios_simulator

net/nqe/network_quality_estimator_unittest.cc

Index: net/nqe/network_quality_estimator_unittest.cc
diff --git a/net/nqe/network_quality_estimator_unittest.cc b/net/nqe/network_quality_estimator_unittest.cc
index 855fbb3327bacdf5e3c9b7ba2f6a147a616bc81c..fcbca2b5a2c8df1d015671b50cf80b21271a44b1 100644
--- a/net/nqe/network_quality_estimator_unittest.cc
+++ b/net/nqe/network_quality_estimator_unittest.cc
@@ -1366,9 +1366,18 @@ TEST(NetworkQualityEstimatorTest, TestThroughputNoRequestOverlap) {
   }
 }
 
+#if defined(OS_IOS)
+// Flaky on iOS: crbug.com/672917.
+#define MAYBE_TestEffectiveConnectionTypeObserver \
+  DISABLED_TestEffectiveConnectionTypeObserver
+#else
+#define MAYBE_TestEffectiveConnectionTypeObserver \
+  TestEffectiveConnectionTypeObserver
+#endif
+
 // Tests that the effective connection type is computed at the specified
 // interval, and that the observers are notified of any change.
-TEST(NetworkQualityEstimatorTest, TestEffectiveConnectionTypeObserver) {
+TEST(NetworkQualityEstimatorTest, MAYBE_TestEffectiveConnectionTypeObserver) {
   base::HistogramTester histogram_tester;
   std::unique_ptr<base::SimpleTestTickClock> tick_clock(
       new base::SimpleTestTickClock());