Always check for GL_ARB_sync
Always check for GL_ARB_sync

Previously, this was only checked for desktop GL, not for GLES. With [1], ANGLE
now exposes GL_ARB_sync for GLES, so we should extend the check. Also always
check for GL_APPLE_sync for consistency. It's technically out-of-spec for
GL_ARB_sync to exist outside of desktop GL, and for GL_APPLE_sync to exist
outside of GLES, but if the platform is listing the extensions, we should expect
them to work anyway.

Bug: chromium: 1028799
Change-Id: I411d2f106df0a2d7eb9b288053478ee79e060b81
R: f5cabf8735907151a446812c9875d6c0c712d847@google.com
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/257693
Commit-Queue: Robert Phillips <95e8ac5504948c7bf91b22c16a8dbb7ae7c66bfd@google.com>
Reviewed-by: Robert Phillips <95e8ac5504948c7bf91b22c16a8dbb7ae7c66bfd@google.com>

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