These are the packages that would be merged, in order:

Calculating dependencies ... done!
Dependency resolution took 1.02 s (backtrack: 0/20).

[ebuild  N     ] media-libs/giflib-6.1.3:0/7::gentoo  USE="-doc -static-libs" 460 KiB
[ebuild  N     ] media-libs/libwebp-1.4.0:0/7::gentoo  USE="gif jpeg opengl png tiff -static-libs -swap-16bit-csp" CPU_FLAGS_X86="sse2 sse4_1" 4182 KiB

Total: 2 packages (2 new), Size of downloads: 4641 KiB