This CL fix the extractBits polyfill, used for D3D12 backend on windows.
With this patch the related CTS would get pass.
Fixed: tint:1775
Change-Id: I15636bb55af502fff773c19f03b4c3c9e99b63fd
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/112207
Reviewed-by: Ben Clayton <bclayton@google.com>
Commit-Queue: Zhaoming Jiang <zhaoming.jiang@intel.com>
Kokoro: Kokoro <noreply+kokoro@google.com>