tree b393217bf96773b365c10c7a5cb71ee4c1ff72a7
parent 95cf7b9b7fbabb77cd341f17da79c947bcc934ab
author Kenny Root <kroot@google.com> 1458323416 -0700
committer Kenny Root <kroot@google.com> 1458341530 -0700

Prefer AES when hardware acceleration is available

ChaCha20-Poly1305 is more efficient in software, but many modern CPUs
have acceleration for AES which makes AES-GCM the more preferable choice
in terms of throughput and battery consumption (i.e., less CPU cycles
per byte).

Use the CPU features as reported by BoringSSL to determine when to
prioritize AES-GCM over ChaCha20-Poly1305. This should be good enough to
say when the trade-off should be made.

(cherry picked from commit 4209803a99fe1c26e5ef66c16dc70e302a428e8a)

Bug: 26945889
Change-Id: I7ae2f3e422e30e83324c08514509cb3e9a506d97