Add proper metric flush

[quentin-cha]

proposed fix for google#1920

[Harwayne]

To be sure I understand, the intention is to only submit vendor/contrib.go.opencensus.io/exporter/stackdriver/stats.go and vendor/go.opencensus.io/metric/metricexport/reader.go, correct? The changes to other files seem to be mostly to speed up triggering the bug, rather than something needed for the fix, and therefore aren't something you intend to submit, right?

If my assumption is correct, then those two vendored files LGTM. I especially appreciate the in-depth comment in stats.go.

[quentin-cha]

To be sure I understand, the intention is to only submit vendor/contrib.go.opencensus.io/exporter/stackdriver/stats.go and vendor/go.opencensus.io/metric/metricexport/reader.go, correct? The changes to other files seem to be mostly to speed up triggering the bug, rather than something needed for the fix, and therefore aren't something you intend to submit, right?

If my assumption is correct, then those two vendored files LGTM. I especially appreciate the in-depth comment in stats.go.

Yes you are correct, only the two .go files in the vendor directories are part of the fix. Thanks for the LGTM

[github-actions]

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