Android Code Search (cs.android.com): The official, free public code search tool provided by Google. It allows developers to search the source code with cross-references, making it easy to navigate by clicking through from one part of the code to another.
Results (average time in minutes):
Porting: Identifying necessary drivers and hardware abstractions for new devices. xref aosp free
The Tech: It uses Kythe, a Google-internal technology for indexing codebases. Android Code Search (cs