Invoke the geolocation callback only if there is pending request.
Invoke the geolocation callback only if there is pending request.

BUG=511338

Review URL: https://codereview.chromium.org/1248803004

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#340194}

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