This CL adds `<<=` and `>>=` to the supported operators in WGSL. The
ExpandCompoundAssignment transform is used to convert to the expanded form.
Bug: tint:1594
Change-Id: I20519052c52d4b69bc90def1acc5c0a30c36fd8a
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/97980
Auto-Submit: Dan Sinclair <dsinclair@chromium.org>
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Dan Sinclair <dsinclair@chromium.org>
Commit-Queue: Ben Clayton <bclayton@google.com>