In editing unit test code, we often need to examine whether a Range/EphemeralRange matches its expectation. Currently, the only way to serialize it is by converting it into a SelectionTemplate, like:

EphemeralRange actual_range = ...;
EXPECT_EQ(
    "<div>bla ^bla| bla</div>",
    GetSelectionTextFromBody(
        SelectionInDOMTree::Builder()
          .SetBaseAndExtent(actual_range)
          .Build()));

It's easier if we can do something like:

EphemeralRange actual_range = ...;
EXPECT_EQ(
    "<div>bla ^bla| bla</div>",
    GetRangeTextFromBody(actual_range));