Fix double move of OnceCallback in GetOperationTask

Interestingly this went unnoticed because of two other problems that
this CL addresses:
* The respective unit test was not using different "operation names"
  when attempting to test two simultaneous requests.
* As the task itself didn't called those callbacks, the unit test
  wouldn't detect the error on its own and DCHECKs were needed in
  PrefetchNetworkRequestFactoryImpl for that.

Bug: 965228
Change-Id: I6aa9bfc7eb3f56e5931d8fc254b2f0de4a911061
Commit-Queue: Carlos Knippschild <>
Reviewed-by: Dan H <>
Cr-Commit-Position: refs/heads/master@{#661863}
8 files changed