WebGPU Kotlin: Added fix for unused variable in Texture helper for g3 blaze test

Bug: 455541592
Change-Id: I8ed9f94df69593409d7130eb1ba67271c9688902
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/269855
Reviewed-by: Tarun Saini <sainitarun@google.com>
Reviewed-by: Nikita Gupta <nikigupta@google.com>
Commit-Queue: Mridul Goyal <mridulgoyal@google.com>
diff --git a/tools/android/webgpu/src/main/java/androidx/webgpu/helper/Textures.kt b/tools/android/webgpu/src/main/java/androidx/webgpu/helper/Textures.kt
index b4109b1..5a46bb9 100644
--- a/tools/android/webgpu/src/main/java/androidx/webgpu/helper/Textures.kt
+++ b/tools/android/webgpu/src/main/java/androidx/webgpu/helper/Textures.kt
@@ -56,7 +56,11 @@
         it.finish()
     }))
 
-    readbackBuffer.mapAsync(MapMode.Read, 0, size.toLong())
+    val bufferMapReturn = readbackBuffer.mapAsync(MapMode.Read, 0, size.toLong())
+
+    if (bufferMapReturn.status != MapAsyncStatus.Success) {
+        throw DawnException("Failed to map buffer: ${bufferMapReturn.message}")
+    }
 
     return Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888).apply {
         copyPixelsFromBuffer(readbackBuffer.getConstMappedRange(size = readbackBuffer.size))