Add labels to Skia OpenGL backend.
Add labels to Skia OpenGL backend.

This CL will add labels to Skia OpenGL backend using ANGLE's
labeling API.

Bug: chromium:1164111
Change-Id: I479f273fdeb2ba719831ab3de778716c9157b433
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/455899
Reviewed-by: Greg Daniel <39df0a804564ccb6cf75f18db79653821f37c1c5@google.com>
Commit-Queue: Greg Daniel <39df0a804564ccb6cf75f18db79653821f37c1c5@google.com>

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