ART: Check for duplicate classes when loading oat files

Oat files are usually produced standalone, and the compilers take
advantage of any information they get. It is thus possible that
when compile-time and runtime class-path are not the same, classes
are resolved differently and optimized code is incorrect.

This is a very conservative check, scanning the complete class tables
of dex files. In case any duplicate class is found, the new oat file
will be rejected and the original dex files will be used in interpreted

A possible refinement to this is actual tracking of the compile-time
class-path instead. That is however significantly complicated by the
DexFile API and the non-standard uses it allows.

An alternative for both optimized code and correct resolution is
native multidex. Apps should switch to multidex and benefit from
the optimization as well as the shift of all compile time to install
time. Split APKs are currently compiled separately, but it is a goal
to change that install flow to simulated multidex.

Change-Id: Ib9e0db5091e060e3bb2c0e5e6c007430becbfc21
20 files changed