AI 143801: am: CL 143779 am: CL 143727 Make the test runner and results assets...

AI 143801: am: CL 143779 am: CL 143727 Make the test runner and results assets of DumpRendertree. This is done so that we could have
  1) Lab machines can run layout tests without having build environment setup
  2) We could have different set of pass/fail results per branch
  Also added a simple python script which runs run_layout_tests.py
  Original author: sridharg
  Merged from: //branches/cupcake/...
  Original author: android-build
  Merged from: //branches/donutburger/...

Automated import of CL 143801