Android: Cache android studio project entries

- Add entry.AllEntries() in preparation for iterating through deps.
- Caching _ProjectEntry objects to avoid duplicate computation.
- Dedup template variables between androidTest and main.
- Minor clean-up.

BUG=620034

Review-Url: https://codereview.chromium.org/2697313004
Cr-Commit-Position: refs/heads/master@{#451352}
2 files changed