Fix performance regression in OatFile::GetOatDexFile().

Try to avoid calculating the canonical location of the
dex file if possible and when we have to calculate it,
cache the lookup result for subsequent lookups.

Bug: 16828525
Bug: 16859671

(cherry picked from commit 3f5838d7d0b9fc63db0ccc35c2ea05ed29264986)

Change-Id: Ifd9a45dada2cc724382fd03c10f6437a6b71e666
3 files changed