Test code that requires test data should call Paths::TestDataRoot() to
obtain the test data root. This will use the CRASHPAD_TEST_DATA_ROOT
environment variable if set. Otherwise, it will look for test data at
known locations relative to the executable path. If the test data is not
found in any of these locations, it falls back to using the working
directory, the same as the current behavior.
BUG=crashpad:4
TEST=crashpad_util_test Paths.TestDataRoot and others
R=rsesek@chromium.org, scottmg@chromium.org
Review URL: https://codereview.chromium.org/992503002
