This has always been the case but it was not obvious from the documentation.
The reason for the quoting is that String() may return an abbreviated string,
starting with double-quote (") but ending in ... (w/o a quote). The missing
quote indicates the abbreviation (in contrast to a string ending in ...").

constant.StringVal can be used to obtain the unquoted string of a String Value.

Change-Id: Id0ba45b6ff62b3e024386ba8d907d6b3a4fcb6d7
Reviewed-on: https://go-review.googlesource.com/28576Reviewed-by: Alan Donovan <adonovan@google.com>