Use the new java_cpp_enum rule in content.

This moves most of the generated Java enums under content/ to use the
java_cpp_enum rule removing the need for keeping the enums in
separate list files and the need for the .template files.

BUG=405532, 351558

Review URL: https://codereview.chromium.org/615893003

Cr-Commit-Position: refs/heads/master@{#297789}
37 files changed