libANGLE: Declare copy operator if copy constructor is defined If the copy constructor is defined then the copy assignment must also be defined, but we can use the default here. v2: Don't inline because the chromium-style errors out on this Bug: angleproject:4486 Change-Id: Iec0f63342244249da32b455b49a0b89b6558cab9 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/2690953 Reviewed-by: Jamie Madill <jmadill@chromium.org> Reviewed-by: Geoff Lang <geofflang@chromium.org> Commit-Queue: Jamie Madill <jmadill@chromium.org>