Add support for stripping Chrome tests.

Add support for stripping Chrome tests.

The chromeos-chrome ebuild strips Chrome tests after the build, but it
can run significantly faster if we strip them during the build. This
changelist reduces the time it takes to build Chrome by allowing
developers to remove unnecessary debug symbols.

Performance comparison on z600 LOCAL_SOURCE build:
  Before: 24m31s (257m04s user, 23m19s sys)
  After:  20m55s (236m12s user, 22m10s sys)

Companion CL for updating Chrome OS to use strip_tests by default is here:
  https://gerrit.chromium.org/gerrit/11517

BUG=chromium-os:22844
TEST=Build with and without debug symbols. Confirm speed difference.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=110948

[DaveMoore, 2011-11-11 18:47:45]

lgtm