Implement BrowserStateKeyedServiceFactory::GetAssociatedPrefRegistry()
As part of this CL, the dependency of //components/user_prefs
on //content is removed.
TBR=rlp, estade
Committed:
https://crrev.com/3b2d62da970372d204fe938da56ee4a662445ba8
Cr-Commit-Position: refs/heads/master@{#325401}