base

Extract pathclassloader initialization to a separate class

To be able to reuse this code when creating a classloader for
the system_server.

Bug: http://b/27245894
Bug: http://b/27702070
Change-Id: I928175a39a1beb0446d863a5b8f5edf94686e768
(cherry picked from commit 5d7d777fa6f47ade2097e77d3d9ddb52c26d77d6)