[Supersize] Add linker_map_parser_test.py and test_util.py.

We plan to update linker_map_parser.py to extract more Level 3 symbols
from .map files. As seen in crbug.com/892648, there are many cases that
need to be handled.

This CL adds linker_map_parser_test.py, which takes the identified
issues from Android Chrome's .map file as test cases. Details:
* Currently focus on ARM (32-bit) builds using LLD with ThinLTO.
* Similar to integration_test.py, the '--update' can be specified to
  overwrite "golden" output files with current output.
  * Add test_util.py to factor common code involving usage and
    management of "golden" files.
* The initial Parser.golden is obtained from running the test for
  unmodified linker_map_parser.py. This allows upcoming parser changes
  to be tracked.

Bug: 892648
Change-Id: Ia8a4dbce4c235f2b08df2bb848409caffcedac32
Reviewed-on: https://chromium-review.googlesource.com/c/1373873
Commit-Queue: agrieve <agrieve@chromium.org>
Reviewed-by: agrieve <agrieve@chromium.org>
Cr-Commit-Position: refs/heads/master@{#616152}
5 files changed