profiler: test TestDeltaMutexProfile fails with Go 1.14beta1

[eclipseo]

Environment
Fedora Rawhide, Go 1.14beta1, cloud 0.51 and 0.52

Code

cloud.google.com/go/profiler
--- FAIL: TestDeltaMutexProfile (2.04s)
    profiler_test.go:868: backgroundHog not in the delta mutex profile (sum=0):
        PeriodType: contentions count
        Period: 1
        Time: 2020-01-29 15:26:46.270877537 +0000 UTC
        Samples:
        contentions/count delay/nanoseconds
             793600  959566780: 1 2 
                700    2304313: 3 2 
        Locations
             1: 0x55dab3d9d580 M=1 sync.(*Mutex).Unlock /usr/lib/golang/src/sync/mutex.go:190 s=0
             2: 0x55dab3da3b28 M=1 cloud.google.com/go/profiler.hog.func1 /builddir/build/BUILD/google-cloud-go-0.52.0/_build/src/cloud.google.com/go/profiler/profiler_test.go:927 s=0
             3: 0x55dab3d9d55f M=1 sync.(*Mutex).Unlock /usr/lib/golang/src/sync/mutex.go:190 s=0
        Mappings
        1: 0x55dab360b000/0x55dab3da6000/0x4a7000 /tmp/go-build963720630/b001/profiler.test 0fdaed16e14eba5df21ec9643c4fce7ee94a99ed [FN]
FAIL
exit status 1
FAIL	cloud.google.com/go/profiler	12.574s

Started to fail on Go 1.14beta1, was working or Go 1.13.5.

[tbpg]

I was able to reproduce this:

Go 1.13:

$ go test -v -run TestDeltaMutexProfile
go: downloading google.golang.org/genproto v0.0.0-20200115191322-ca5a22157cba
go: extracting google.golang.org/genproto v0.0.0-20200115191322-ca5a22157cba
go: finding google.golang.org/genproto v0.0.0-20200115191322-ca5a22157cba
=== RUN   TestDeltaMutexProfile
--- PASS: TestDeltaMutexProfile (2.10s)
PASS
ok  	cloud.google.com/go/profiler	2.198s

Go 1.14beta1:

$ go1.14beta1 test -v -run TestDeltaMutexProfile           
=== RUN   TestDeltaMutexProfile
    TestDeltaMutexProfile: profiler_test.go:868: backgroundHog not in the delta mutex profile (sum=0):
        PeriodType: contentions count
        Period: 1
        Time: 2020-01-29 11:23:19.673458092 -0500 EST
        Samples:
        contentions/count delay/nanoseconds
             869700 1054401211: 1 2 
               1100    2516636: 3 2 
        Locations
             1: 0xb8e09e M=1 sync.(*Mutex).Unlock /usr/local/google/home/tbp/sdk/go1.14beta1/src/sync/mutex.go:190 s=0
             2: 0xb945f6 M=1 cloud.google.com/go/profiler.hog.func1 /usr/local/google/home/tbp/go/src/cloud.google.com/go/profiler/profiler_test.go:927 s=0
             3: 0xb8e07d M=1 sync.(*Mutex).Unlock /usr/local/google/home/tbp/sdk/go1.14beta1/src/sync/mutex.go:190 s=0
        Mappings
        1: 0x400000/0xb96000/0x0 /tmp/go-build528717842/b001/profiler.test  [FN]
--- FAIL: TestDeltaMutexProfile (2.02s)
FAIL
exit status 1
FAIL	cloud.google.com/go/profiler	2.120s

[tbpg]

I reported golang/go#36874 since this seems to be a change in the behavior of Go.

The call to symbolize is the problem. But, I think we can delete it since the workaround is not needed yet. I'll send a CL. Edit: assigning to @jqll, who's worked on this in the past.

[jqll]

Mutex profile is probably now symbolized. https://github.com/googleapis/google-cloud-go/blob/master/profiler/profiler.go#L442 needs to check if the profile is already symbolized. I can work on a fix probably later today.