Use the ExpandCompoundAssignment transform to convert compound
assignments to regular assignments.
Bug: tint:1325
Change-Id: Ic843964ec24d8a2f00f801823f8f8bbf1c6fab5c
Reviewed-on: https://dawn-review.googlesource.com/c/tint/+/85284
Reviewed-by: Ben Clayton <bclayton@google.com>
Kokoro: Kokoro <noreply+kokoro@google.com>