[ObjC ARC] Converts ios/chrome/browser/device_sharing:eg_tests to ARC.

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

Review-Url: https://codereview.chromium.org/2627633002
Cr-Commit-Position: refs/heads/master@{#442859}

ios/chrome/browser/device_sharing/BUILD.gn

@@ -39,6 +39,7 @@ source_set("unit_tests") {
 }
 
 source_set("eg_tests") {
+  configs += [ "//build/config/compiler:enable_arc" ]
   testonly = true
   sources = [
     "handoff_manager_egtest.mm",

ios/chrome/browser/device_sharing/handoff_manager_egtest.mm

@@ -17,6 +17,10 @@
 #import "net/base/mac/url_conversions.h"
 #include "url/gurl.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 
 // Checks that Handoff will report the specified |gurl|.