Add GrTAllocator::push_back(T&&)

Allow push_back to take an rvalue to move into the allocator, which has
the nice side effect of making the test for it a bit better.

Change-Id: I7e313cf75c1ad65fbf765b10c4717672063b5570
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/280412
Reviewed-by: Michael Ludwig <michaelludwig@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
2 files changed