SkTHashTable assert key self equal.
SkTHashTable assert key self equal.

Add an assert in SkTHashTable::uncheckedSet that each added key is equal
to itself. This is an implied precondition which is easy to get wrong if
the key contains floating point values which may become NaN.

Motivated by https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=30314
which would have been much easier to track down with this assert, since
the issue would have been discovered at insertion instead of much later
on removal.

Change-Id: I4eabb6892d2bff1e7bc33c04fd6b297b189a3b02
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/405695
Reviewed-by: Herb Derby <9e12a3d2bbf73546e47cc9958f6ba8f3215b7eaf@google.com>
Commit-Queue: Ben Wagner <53965154ffeecc4a10886eab9259e95965f2979a@google.com>

google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia,google/skia,google/skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,google/skia