WebGPU: Report more details about buffer map async status

This patch replaces the "unknown" buffer map async status with
two more detailed ones (destroyed_before_callback and
ummapped_before_callback) to provide more information about
these abnormal buffer may async statuses.

BUG=dawn:533

Change-Id: I17480eb87b7af5ef131e37843ad37097ad4f5026
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2434110
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#811640}

third_party/blink/renderer/modules/webgpu/gpu_buffer.cc

@@ -291,6 +291,16 @@ void GPUBuffer::OnMapAsyncCallback(ScriptPromiseResolver* resolver,
       resolver->Reject(MakeGarbageCollected<DOMException>(
           DOMExceptionCode::kOperationError, "Device is lost"));
       break;
+    case WGPUBufferMapAsyncStatus_DestroyedBeforeCallback:
+      resolver->Reject(MakeGarbageCollected<DOMException>(
+          DOMExceptionCode::kOperationError,
+          "Buffer is destroyed before the mapping is resolved"));
+      break;
+    case WGPUBufferMapAsyncStatus_UnmappedBeforeCallback:
+      resolver->Reject(MakeGarbageCollected<DOMException>(
+          DOMExceptionCode::kOperationError,
+          "Buffer is unmapped before the mapping is resolved"));
+      break;
     default:
       NOTREACHED();
   }