Allow for ExtensionSetting subpolicies with multiple extensions as a key

Bug: 949274
Change-Id: Ie7accffe2336d9b616267d898ff8c8a4bb9f4ecc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1548379
Commit-Queue: Kyle Spiers <[email protected]>
Reviewed-by: Devlin <[email protected]>
Reviewed-by: Lutz Justen <[email protected]>
Cr-Commit-Position: refs/heads/master@{#650121}
3 files changed