Now, that presumed, when an author contributes to the project, they explicitly agree to license their contributions under to the project's BSD license.
However, Google owns this code being contributed, and yet they, as a corporate entity, have not consented to the licensing of their contributions being distributed under the BSD license. Until they do, in writing, signed by the corporate legal counsel, or whoever else is able to sign contracts on their behalf, the code contributed is not BSD licensed because the author, which is Google Inc, did not agree to it in writing, and thus distribution and use is now a violation of Google's copyright since they did not legally consent to have their code released. As the owner of the code, Google alone can consent to its use, and not the "code slave resource" who happened to produce it, whose very soul Google now contractually owns.
This could be a problem for the project.
In general, projects need to require that anyone contributing new code represent that they alone are the owners of the copyright to the new code being contributed. If you contribute code owned by someone else and not explicitly licensed in a compatible manner by that other entity, then you have code in the project that presents a serious legal liability.