[ObjC ARC] Converts ios/chrome/browser/web:unit_tests_internal to ARC.

ios/chrome/browser/web/external_app_launcher_unittest.mm

 // Copyright 2014 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.
 
 #include "ios/chrome/browser/web/external_app_launcher.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "testing/gtest_mac.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @interface ExternalAppLauncher (Private)
 // Returns the Phone/FaceTime call argument from |url|.
 // Made available for unit testing.
 + (NSString*)formatCallArgument:(NSURL*)url;
 @end
 
 namespace {
 
 TEST(ExternalAppLauncherTest, TestBadFormatCallArgument) {
   EXPECT_NSEQ(@"garbage:",
@@ skipping 23 matching lines @@
 }
 
 TEST(ExternalAppLauncherTest, TestURLEscapedArgument) {
   EXPECT_NSEQ(@"+1 650 555 1212",
               [ExternalAppLauncher
                   formatCallArgument:
                       [NSURL URLWithString:@"tel://+1%20650%20555%201212"]]);
 }
 
 }  // namespace