I'm happy to announce that working with the Verible project codebase has become a lot easier.
https://cs.opensource.google/verible/verible (bookmark me!) provides a fully indexed search and navigation for C++. Definitions and references are just a click away. The search bar displays suggestions as you type (and features rich query atoms). Source code views can also show blame/annotate layers, helping you find commits related to specific features/fixes/tests.
Huge props to
Tim Ansell for leading this effort internally, and
Mina Toma for early work demonstrating indexing of the Verible codebase using Kythe.
Happy coding!