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

ios/chrome/browser/metrics/tab_usage_recorder_egtest.mm

Index: ios/chrome/browser/metrics/tab_usage_recorder_egtest.mm
diff --git a/ios/chrome/browser/metrics/tab_usage_recorder_egtest.mm b/ios/chrome/browser/metrics/tab_usage_recorder_egtest.mm
index 4412291e4cb52447680e2025ecc46ac2c7a7c88e..c6d6aaa843777f6883713e12b96bd8c5c572d905 100644
--- a/ios/chrome/browser/metrics/tab_usage_recorder_egtest.mm
+++ b/ios/chrome/browser/metrics/tab_usage_recorder_egtest.mm
@@ -40,6 +40,10 @@
 #include "ui/base/l10n/l10n_util.h"
 #include "ui/base/l10n/l10n_util_mac.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 namespace {
 
 const char kTestUrl1[] =
@@ -336,7 +340,7 @@ void SelectTabUsingUI(NSString* title) {
     __block bool finished = false;
     chrome_test_util::GetCurrentWebState()->ExecuteJavaScript(
         base::UTF8ToUTF16(kClearPageScript),
-        base::BindBlock(^(const base::Value*) {
+        base::BindBlockArc(^(const base::Value*) {
           finished = true;
         }));