[ Merge of http://go/wvgerrit/120512 ]
Wrapped DRM private keys are loaded when a key request is made or when
offline/usage sessions are restored. They were earlier loaded when a
session was opened.
For streaming sessions, key material will be fetched from the default
or legacy certificates and loaded when a key request is made.
For offline and usage sessions, key material may be retrieved from
license or usage records if available. If not available, information
associated with the legacy certificate will be loaded.
Certificate and wrapped keys are also written out when an offline
license or usage record is saved.
Bug: 169740403
Test: WV unit/integration tests
WvCdmRequestLicenseTest.ProvisioningWithExpiringCertTest
WvCdmRequestLicenseTest.StreamingWithExpiringCertTest
WvCdmRequestLicenseTest.RestoreOfflineKeysWithExpiringCertTest
Change-Id: Ice0154c632170c46da171cbbb23a97380c610a98
e538c96131