[ObjC ARC] Converts ios/chrome/test/ocmock:ocmock to ARC.

ios/chrome/test/ocmock/OCMockObject+BreakpadControllerTesting.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.
 
 #import "ios/chrome/test/ocmock/OCMockObject+BreakpadControllerTesting.h"
 
 #import "breakpad/src/client/ios/BreakpadController.h"
 #include "testing/gtest/include/gtest/gtest.h"
 #import "third_party/ocmock/OCMock/OCMock.h"
 
+#if !defined(__has_feature) || !__has_feature(objc_arc)
+#error "This file requires ARC support."
+#endif
+
 @implementation OCMockObject (BreakpadControllerTesting)
 
 - (void)cr_expectGetCrashReportCount:(int)crashReportCount {
   id invocationBlock = ^(NSInvocation* invocation) {
-    void (^block)(int);
+    __unsafe_unretained void (^block)(int);
     [invocation getArgument:&block atIndex:2];
     if (!block) {
       ADD_FAILURE();
       return;
     }
     block(crashReportCount);
   };
   BreakpadController* breakpadController =
       static_cast<BreakpadController*>([[self expect] andDo:invocationBlock]);
   [breakpadController getCrashReportCount:[OCMArg isNotNil]];
 }
 
 @end