libchromeos: add GetOrDefault to map_utils

Adds a helper that, given a key, returns the value from a std::map if the key is
set and a default value if it is not.

BUG=None
TEST=FEATURES=test emerge-gizmo libchromeos

Change-Id: I629b4389644b1e90db3e9802122918b55ac3e778
Reviewed-on: https://chromium-review.googlesource.com/235490
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>
Commit-Queue: Bertrand Simonnet <bsimonnet@chromium.org>
Tested-by: Bertrand Simonnet <bsimonnet@chromium.org>
1 file changed