fixup! Use mojom::ManifestImageResource_Purpose instead of ImageResource::Purpose

The original CL missed removing unnecessary enum conversion in
Manifest's TypeCoverter::Convert().

Bug: 919392
Change-Id: I0cf7f217c9cf60a1b94c42e243d0fe04e9fa224d
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2577395Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Commit-Queue: Gyuyoung Kim <gyuyoung@igalia.com>
Cr-Commit-Position: refs/heads/master@{#834711}

third_party/blink/renderer/modules/manifest/manifest_type_converters.cc

@@ -96,15 +96,8 @@ TypeConverter<blink::Manifest::ImageResource,
   for (auto& size : input->sizes)
     output.sizes.push_back(gfx::Size(size));
 
-  for (auto purpose : input->purpose) {
-    blink::mojom::ManifestImageResource_Purpose out_purpose;
-    if (!EnumTraits<blink::mojom::ManifestImageResource_Purpose,
-                    ::blink::mojom::ManifestImageResource_Purpose>::
-            FromMojom(purpose, &out_purpose)) {
-      NOTREACHED();
-    }
-    output.purpose.push_back(out_purpose);
-  }
+  for (auto purpose : input->purpose)
+    output.purpose.push_back(purpose);
 
   return output;
 }