Add comment to IPC_ENUM_TRAITS call

Add comment to IPC_ENUM_TRAITS call to indicate we are dealing with a
bitmask, this is consistent with other call sites for IPC_ENUM_TRAITS.

Bug: 246708
Change-Id: I5f979772fc82ed6bdf19f0eda31781c7ffee2e13
Reviewed-on: https://chromium-review.googlesource.com/761268
Reviewed-by: Bill Budge <[email protected]>
Reviewed-by: Tom Sepez <[email protected]>
Commit-Queue: Rob Buis <[email protected]>
Cr-Commit-Position: refs/heads/master@{#515594}
1 file changed