The official Bazel packages for Debian/Ubuntu depend on java8-sdk, which usually resolves to openjdk-8-jdk. This is the full JDK including graphical toolkits, and it's fairly bulky when working within a Docker container:

$ apt-get install --no-install-recommends openjdk-8-jdk
[...]
Need to get 72.8 MB of archives.
After this operation, 384 MB of additional disk space will be used.

Since Bazel doesn't have a graphical component, it would be nice if it depended on java8-sdk-headless, which is less than half as big:

$ apt-get install --no-install-recommends openjdk-8-jdk-headless
[...]
Need to get 39.8 MB of archives.
After this operation, 155 MB of additional disk space will be used.