capture.output() duplicates last line unless newline (R-devel bug)

In R-devel (2015-08-12 r69024), capture.output() incorrectly
duplicates the last line unless it ends with a newline.  I don't see
this in R 3.2.2 RC (2015-08-13 r69049).  It seems to have started
fairily recently; I spotted this yesterday after starting to get
errors in my R.utils check that use capture.output(), cf.
https://www.r-project.org/nosvn/R.check/r-devel-linux-x86_64-debian-clang/R.utils-00check.html

Examples:

x <- "a"
cat(x)

a>

capture.output(cat(x))

[1] "a" "a"

x <- "a\n"
cat(x)

a

capture.output(cat(x))

[1] "a"

x <- "a\nb"
cat(x)

a
b>

capture.output(cat(x))

[1] "a" "b" "b"

x <- "a\nb\n"
cat(x)

a
b

capture.output(cat(x))

[1] "a" "b"

capture.output(cat(x))

[1] "a" "b"

x <- c("a", "b")
cat(x)

a b>

capture.output(cat(x))

[1] "a b" "a b"

x <- c("a", "b\n")
cat(x)

a b

capture.output(cat(x))

[1] "a b"

sessionInfo()

R Under development (unstable) (2015-08-12 r69024)
Platform: x86_64-w64-mingw32/x64 (64-bit)
Running under: Windows 7 x64 (build 7601) Service Pack 1

locale:
[1] LC_COLLATE=English_United States.1252
[2] LC_CTYPE=English_United States.1252
[3] LC_MONETARY=English_United States.1252
[4] LC_NUMERIC=C
[5] LC_TIME=English_United States.1252

attached base packages:
[1] stats     graphics  grDevices utils     datasets  methods   base

other attached packages:
[1] R.utils_2.1.0-9000     R.oo_1.19.0-9000       R.methodsS3_1.7.0-9000

loaded via a namespace (and not attached):
[1] tools_3.3.0

/Henrik