Remove unnecessary ctors now that we have C++17 copy-elision.

This CL backs out C++14 compatibility changes from
http://review.skia.org/457298 :

"2. Lack of C++17 copy elision means classes of objects constructed at
function return need a copy or move constructor even if RVO will mean it
isn't called."

Change-Id: I33a833d33b221e757bf6a6459835a7215b4e6b66
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/501240
Reviewed-by: Ben Wagner <bungeman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
18 files changed