Fix ClipData JavaDoc and behavior that contradicts JavaDoc

1. Expand JavaDoc for ClipData.addItem to clarify how MIME types are affected.
2. Add "text/uri-list" to MIME type list only for non-content URIs (as JavaDoc explicitly says).

Bug: 28564003
Change-Id: I074daf34310323725690a9ba2c7dff0542ed6349
1 file changed