Avoid mExtensions for initializing mExtensions tracks the currently enabled extensions, while nativeExtensions tracks which extensions are available on a platform. This makes nativeExtensions more suitable for initializing data, as extensions may be disabled at initialization and enabled later. Bug: angleproject:7769 Change-Id: I9ee821a931045fc89091473f35e2b306ee653613 Reviewed-on: https://chromium-review.googlesource.com/c/angle/angle/+/3965610 Reviewed-by: Geoff Lang <geofflang@chromium.org> Reviewed-by: Cody Northrop <cnorthrop@google.com> Commit-Queue: Sean Risser <srisser@google.com>