Extra stream metadata in stored manifests in v2.5.x and master

[joeyparrish]

Have you read the FAQ and checked for duplicate open issues?
Yes

What version of Shaka Player are you using?
v2.5.9 and master

Can you reproduce the issue with our latest release version?
Yes

Can you reproduce the issue with the latest code from master?
Yes

Are you using the demo app or your own custom app?
Demo app

What browser and OS are you using?
Chrome stable 80 on Linux

What are the manifest and license server URIs?
"Heliocentrism" from the demo app

What did you do?

Store "Heliocentrism" offline

What did you expect to happen?
The IDB metadata for the stored manifest should contain only one stream per period.

What actually happened?
Each of the 3 periods contains metadata for the streams of all 3 periods. Ex:

This issue affects v2.5.0 - v2.5.9, but not v2.4.