Cleanup constructors for SkTDArray

Move the default constructor implementation to .cpp. Remove assign().
Simplify the assigning constructor. Have operator=(const &) use the
assigning constructor.

Change-Id: I916eb4d42a00fc035d29589c166e296f176870fe
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/587544
Commit-Queue: Herb Derby <herb@google.com>
Reviewed-by: John Stiles <johnstiles@google.com>
2 files changed