EME: Fix the CDM File IO test when run using unprefixed EME.
This test was not registering the unprefixed event handlers, processing the
message as the correct type, or enabling required peristent storage capability.
The two FileIOTest tests may still not be testing both paths, but the prefixed
path will be removed in my next CL.
BUG=249976
TEST=ECKEncryptedMediaTest.FileIOTest passes when prefixed EME is manually disabled in the test.
Review URL: https://codereview.chromium.org/1717033002
Cr-Commit-Position: refs/heads/master@{#376601}
3 files changed
