- adding tests to improve coverage of the splice method

BUG=

Committed: https://crrev.com/8533d4b5433d3a9e9fb1015f206997bd6d869fe3
Cr-Commit-Position: refs/heads/master@{#30269}

Review URL: https://codereview.chromium.org/1293683005

Cr-Commit-Position: refs/heads/master@{#30326}