[ObjC ARC] Converts ios/chrome/app:unit_tests to ARC.

ios/chrome/app/deferred_initialization_runner_unittest.mm

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ios/chrome/app/deferred_initialization_runner.h"
 
 #import "base/test/ios/wait_util.h"
 #include "base/time/time.h"
 #include "testing/platform_test.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 TEST(DeferredInitializationRunnerTest, TestSharedInstance) {
   EXPECT_TRUE([DeferredInitializationRunner sharedInstance]);
   // Cancelling a non-existing block does nothing.
   [[DeferredInitializationRunner sharedInstance]
       cancelBlockNamed:@"Invalid Name"];
 }
 
 // Tests that all blocks added on the queue are executed after a delay.
 TEST(DeferredInitializationRunnerTest, TestRunBlockSequentially) {
   // Setup.
@@ skipping 134 matching lines @@
   // Action.
   [runner enqueueBlockNamed:@"multiple" block:runBlock];
   [runner enqueueBlockNamed:@"multiple" block:runBlock];
 
   // Test: |runBlock| was executed only once.
   EXPECT_EQ(1U, [runner numberOfBlocksRemaining]);
   [runner runBlockIfNecessary:@"multiple"];
   EXPECT_EQ(0U, [runner numberOfBlocksRemaining]);
   EXPECT_EQ(1, blockRunCount);
 }