Add nullness annotation to the filed "holder" in Streams.
Add nullness annotation to the filed "holder" in Streams.

RELNOTES=n/a.

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Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=180206224

typetools/guava,Xaerxess/guava,google/guava,EdwardLee03/guava,xasx/guava,EdwardLee03/guava,rgoldberg/guava,typetools/guava,Xaerxess/guava,mosoft521/guava,xasx/guava,mosoft521/guava,google/guava,google/guava,rgoldberg/guava,berndhopp/guava,berndhopp/guava,mosoft521/guava