There doesn't seem to be an authoritative list for Android, but I did find this: https://android.googlesource.com/platform/libcore2/+/master/... -- not sure whether it means it's in the latest versions of Android, or whether that means it's going to be all versions of Android (e.g. with manufacturer/carrier modifications, etc) or what...
While the vast majority of users upgrade to iOS 8, certainly not everybody does, so it's good to know that iOS 5 (I didn't check any earlier) also includes the "DST Root CA X3" certificate:
https://support.apple.com/en-gb/HT201388
EDIT: I can't find it on my Android phone (4.3)...
EDIT2: Found it! Was added in 2010 under the name Digital Signature Trust.
https://android.googlesource.com/platform/libcore/+/master/l...