Bin packing the zygote (best fit).

We now use bin packing to fill holes in the non movable space with
objects from the bump pointer space when we create the zygote.

Zygote space PSS reduction on AOSP: ~300k.
Zygote size on AOSP: 2121040 bytes -> 1597944 bytes.

Deleted some unreachable code.

Bug: 11902311

Change-Id: Idc957d69e93b3a941e0c298d47a21b73526dd286
4 files changed