refactor(oauth2): add current time injection point for testing

[scotthart]

fixes #8288

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This change is 

[google-cloud-cpp-bot]

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[codecov]

Codecov Report

Merging #8445 (7b67f1e) into main (df6fa36) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##             main    #8445      +/-   ##
==========================================
- Coverage   95.09%   95.09%   -0.01%     
==========================================
  Files        1367     1367              
  Lines      122501   122520      +19     
==========================================
+ Hits       116491   116508      +17     
- Misses       6010     6012       +2     

Impacted Files	Coverage Δ
...oud/internal/oauth2_authorized_user_credentials.cc	100.00% <100.00%> (ø)
...loud/internal/oauth2_compute_engine_credentials.cc	100.00% <100.00%> (ø)
.../internal/oauth2_refreshing_credentials_wrapper.cc	100.00% <100.00%> (ø)
...rnal/oauth2_refreshing_credentials_wrapper_test.cc	100.00% <100.00%> (ø)
...oud/internal/oauth2_service_account_credentials.cc	97.32% <100.00%> (ø)
google/cloud/bigtable/internal/common_client.h	94.02% <0.00%> (-5.98%)	⬇️
google/cloud/storage/internal/curl_handle.h	80.00% <0.00%> (-2.86%)	⬇️
...cloud/pubsub/internal/subscription_session_test.cc	97.75% <0.00%> (-0.25%)	⬇️
google/cloud/pubsub/samples/samples.cc	92.02% <0.00%> (-0.08%)	⬇️
.../cloud/storage/benchmarks/throughput_experiment.cc	74.87% <0.00%> (+0.50%)	⬆️
... and 3 more

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[coryan]

Thanks, it seems that the now parameter becomes redundant? Your call.

[scotthart]

Reviewable status: 0 of 6 files reviewed, 1 unresolved discussion (waiting on @coryan)

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google/cloud/internal/oauth2_refreshing_credentials_wrapper.cc, line 26 at r1 (raw file):

Previously, coryan (Carlos O'Ryan) wrote…

Thanks, it seems that the now parameter becomes redundant? Your call.

Removed the now parameter and just calling current_time_fn where needed.

[google-cloud-cpp-bot]

Google Cloud Build Logs
For commit: 7b67f1e3b98f5961ad7142b55f6118596723354e

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[coryan]

Reviewed 6 of 6 files at r2, all commit messages.
Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @scotthart)

[coryan]

Reviewable status: complete! all files reviewed, all discussions resolved (waiting on @scotthart)