Allow users set cache dir for each image.
Test: run crosperf without setting cache_dir,
                   setting cache_dir globally
                   setting cache_dir globally and in label at the same
                           time
                   setting cache_dir in label only
      All pass.

PRESUBMIT=passed
R=llozano,shenhan,carrot
APPROVED=shenhan
DELTA=28  (13 added, 5 deleted, 10 changed)
OCL=65663-p2
RCL=65666-p2
RDATE=2013/02/05 12:31:42


P4 change: 42807185
7 files changed
tree: b38b1a4eb01581ec17e89e2079c8d082aa3b857e
  1. .git5_specs/
  2. v14/