use whitelist for selecting observed values (#25974)
Summary:
Pull Request resolved: https://github.com/pytorch/pytorch/pull/25974
Previously we observe all the Tensor values, but what we want is actually
observing only the ones that can be quantized.
Test Plan:
python test/test_jit.py
python test/test_quantizer.py
Imported from OSS
Differential Revision: D17348986
fbshipit-source-id: 55be0d73862a0e7eb1e7fd882d16e0d830618b63
