There are 64 tests that are failing every second run on Android Cronet Marshmallow 64bit Builder: https://build.chromium.org/p/chromium.android/builders/Android%20Cronet%20Marshmallow%2064bit%20Builder/builds/1385/steps/net_unittests/logs/stdio
The tests are passing on other bots.

From the log:
C  443.332s Main  Summary
C  443.332s Main  ********************************************************************************
C  443.365s Main  [==========] 15535 tests ran.
C  443.365s Main  [  PASSED  ] 15471 tests.
C  443.365s Main  [  FAILED  ] 64 tests, listed below:
C  443.365s Main  [  FAILED  ] UDPSocketTest.ConnectRandomBind (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLFetcherBadHTTPSTest.BadHTTPS (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLFetcherTest.CancelInDownloadProgressCallback (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLFetcherTest.FileTestOverwriteExisting (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLFetcherTest.PostEntireFile (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLFetcherTest.ReuseFetcherForSameURL (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLFetcherTest.TempFileTestTakeOwnership (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestContextBuilderTest.UserAgent (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestHttpJobTest.TestCancelWhileReadingCookies (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestHttpJobWithMockSocketsTest.TestNetworkBytesCancelledImmediately (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestInterceptorTest.InterceptLoadTimingEarlyProxyResolutionReused (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestInterceptorTest.InterceptRestartRequired (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestSimpleJobTest.CancelAfterFirstReadStarted (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestTest.AcceptClockSkewCookieWithWrongDateTimezone (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestTest.DoNotSaveEmptyCookies (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestTest.NetworkAccessedSetOnHostResolutionFailure (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestTest.SetJobPriority (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestTestHTTP.BasicAuthWithCookies (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestTestHTTP.CancelTest5 (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestTestHTTP.EmptyAcceptLanguage (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestTestHTTP.GetTest_NoCache (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestTestHTTP.NetworkCancelAfterCreateTransactionFailsTest (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestTestHTTP.NetworkDelegateCancelRequestSynchronously3 (UNKNOWN)
C  443.365s Main  [  FAILED  ] URLRequestTestHTTP.NetworkDelegateOnAuthRequiredAsyncCancel (UNKNOWN)
C  443.366s Main  [  FAILED  ] URLRequestTestHTTP.NetworkDelegateRedirectRequest (UNKNOWN)
C  443.366s Main  [  FAILED  ] URLRequestTestHTTP.NoRedirectOn308WithoutLocationHeader (UNKNOWN)
C  443.366s Main  [  FAILED  ] URLRequestTestHTTP.PostEmptyTest (UNKNOWN)
C  443.366s Main  [  FAILED  ] URLRequestTestHTTP.ProcessSTS (UNKNOWN)
C  443.366s Main  [  FAILED  ] URLRequestTestHTTP.RawBodyBytesNoContentEncoding (UNKNOWN)
C  443.366s Main  [  FAILED  ] URLRequestTestHTTP.RedirectLoadTiming (UNKNOWN)
C  443.366s Main  [  FAILED  ] URLRequestTestHTTP.ResponseHeadersTest (UNKNOWN)
C  443.366s Main  [  FAILED  ] URLRequestTestHTTP.URLRequestDelegateInfo (UNKNOWN)
C  443.366s Main  [  FAILED  ] URLRequestTestHTTP.VaryHeader (UNKNOWN)
C  443.366s Main  [  FAILED  ] URLRequestThrottlerEntryTest.InterfaceDuringExponentialBackoff (UNKNOWN)
C  443.366s Main  [  FAILED  ] URLRequestThrottlerEntryTest.SlidingWindow (UNKNOWN)
C  443.366s Main  [  FAILED  ] URLSecurityManager.CanDelegate (UNKNOWN)
C  443.366s Main  [  FAILED  ] UnixDomainClientSocketTest.DisconnectFromClient (UNKNOWN)
C  443.366s Main  [  FAILED  ] UnixDomainServerSocketTest.UnimplementedMethodsFail (UNKNOWN)
C  443.366s Main  [  FAILED  ] UploadBytesElementReaderTest.MultipleInit (UNKNOWN)
C  443.366s Main  [  FAILED  ] UploadFileElementReaderTest.Range (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/PkitsTest01SignatureVerification/0.Section1ValidSignaturesTest1 (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/PkitsTest02ValidityPeriods/0.Section2Validpre2000UTCnotBeforeDateTest3 (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/PkitsTest03VerifyingNameChaining/0.Section3ValidRFC3280OptionalAttributeTypesTest8 (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/PkitsTest06VerifyingBasicConstraints/0.Section6InvalidpathLenConstraintTest10 (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/PkitsTest06VerifyingBasicConstraints/0.Section6ValidbasicConstraintsNotCriticalTest4 (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/PkitsTest13NameConstraints/0.Section13InvalidDNSnameConstraintsTest31 (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/PkitsTest13NameConstraints/0.Section13InvalidDNnameConstraintsTest15 (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/PkitsTest13NameConstraints/0.Section13InvalidRFC822nameConstraintsTest22 (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/PkitsTest13NameConstraints/0.Section13ValidDNnameConstraintsTest1 (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/PkitsTest16PrivateCertificateExtensions/0.Section16InvalidUnknownCriticalCertificateExtensionTest2 (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/VerifyCertificateChainSingleRootTest/0.ExpiredTarget (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/VerifyCertificateChainSingleRootTest/0.IntermediateSignedWithMd5 (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/VerifyCertificateChainSingleRootTest/0.KeyRolloverRolloverChain (UNKNOWN)
C  443.366s Main  [  FAILED  ] VerifyCertificateChain/VerifyCertificateChainSingleRootTest/0.TargetSignedWithMd5 (UNKNOWN)
C  443.367s Main  [  FAILED  ] VerifyCertificateChain/VerifyCertificateChainSingleRootTest/0.ViolatesPathlen1UnconstrainedRoot (UNKNOWN)
C  443.367s Main  [  FAILED  ] VerifyName/CertVerifyProcNameTest.VerifyCertName/4 (UNKNOWN)
C  443.367s Main  [  FAILED  ] VerifyNameMatchInvalidDataTest.FailOnAttributeTypeAndValueEmpty (UNKNOWN)
C  443.367s Main  [  FAILED  ] VerifyNameMatchInvalidDataTest.FailOnInvalidPrintableStringChars (UNKNOWN)
C  443.367s Main  [  FAILED  ] VerifySignedDataTest.EcdsaPrime256v1Sha512UsingEcdhKey (UNKNOWN)
C  443.367s Main  [  FAILED  ] VerifySignedDataTest.PolicyIsAcceptableDigestAlgorithm (UNKNOWN)
C  443.367s Main  [  FAILED  ] VerifySignedDataTest.RsaPkcs1Sha1WrongAlgorithm (UNKNOWN)
C  443.367s Main  [  FAILED  ] VerifySignedDataTest.RsaPssSha1WrongSalt (UNKNOWN)
C  443.367s Main  [  FAILED  ] Version/BidirectionalStreamQuicImplTest.CoalesceDataBuffersNotHeadersFrame/1 (UNKNOWN)
C  443.367s Main  [  FAILED  ] Version/BidirectionalStreamQuicImplTest.DeleteStreamAfterReadData/2 (UNKNOWN)
C  443.367s Main  
C  443.367s Main  64 FAILED TESTS