runtime/pprof: TestCPUProfileMultithreaded is flaky in android/arm

[hyangah]

Note that the number of samples the test observed is small small (18 samples) compared to the test execution time (0.49s). The expected CPU sampling rate is 100Hz.

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http://build.golang.org/log/790f12ebfd076cb47d01055b7ee138b6d40be2b1

go_android_exec: adb shell mkdir -p /data/local/tmp/pprof.test-23878
go_android_exec: adb push /tmp/go-build624543768/runtime/pprof/_test/pprof.test /data/local/tmp/pprof.test-23878/pprof.test-23878-tmp
217 KB/s (3129500 bytes in 14.033s)
go_android_exec: adb shell cp '/data/local/tmp/pprof.test-23878/pprof.test-23878-tmp' '/data/local/tmp/pprof.test-23878/pprof.test-23878'
go_android_exec: adb shell rm '/data/local/tmp/pprof.test-23878/pprof.test-23878-tmp'
go_android_exec: adb shell export TMPDIR="/data/local/tmp/pprof.test-23878"; export GOROOT="/data/local/tmp/goroot"; export GOPATH="/data/local/tmp/gopath"; cd "/data/local/tmp/goroot/src/runtime/pprof"; '/data/local/tmp/pprof.test-23878/pprof.test-23878' -test.short=true -test.timeout=4m0s; echo -n exitcode=$?
--- FAIL: TestCPUProfileMultithreaded (0.49s)
pprof_test.go:161: total 18 CPU profile samples collected
pprof_test.go:170: runtime/pprof_test.cpuHog1: 0
pprof_test.go:170: runtime/pprof_test.cpuHog2: 18
pprof_test.go:184: runtime/pprof_test.cpuHog1 has 0 samples out of 18, want at least 1, ideally 9
FAIL
exitcode=1go_android_exec: adb shell rm -rf /data/local/tmp/pprof.test-23878

[hyangah]

duplicate of #9605.