[ObjC ARC] Converts ios/chrome/browser/ui/collection_view/cells:test_support to ARC.

Automatically generated ARCMigrate commit
Notable issues:None
BUG=624363
TEST=None

Review-Url: https://codereview.chromium.org/2742783002
Cr-Commit-Position: refs/heads/master@{#455762}

ios/chrome/browser/ui/collection_view/cells/BUILD.gn

@@ -41,6 +41,7 @@ source_set("cells") {
 }
 
 source_set("test_support") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "test_utils.h",

ios/chrome/browser/ui/collection_view/cells/test_utils.mm

@@ -4,6 +4,10 @@
 
 #import "ios/chrome/browser/ui/collection_view/cells/test_utils.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace ios_internal {
 
 UIImage* CollectionViewTestImage() {