ios: Stop using __weak.

base/ios/crb_protocol_observers_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.
 
 #import "base/ios/crb_protocol_observers.h"
 #include "base/ios/weak_nsobject.h"
 #include "base/logging.h"
 #include "base/mac/scoped_nsautorelease_pool.h"
 #include "base/mac/scoped_nsobject.h"
 #include "testing/gtest/include/gtest/gtest.h"
@@ skipping 237 matching lines @@
 }
 
 - (void)reset {
   [super reset];
   _optionalMethodInvoked = NO;
 }
 
 @end
 
 @implementation TestMutateObserver {
-  __weak id _observers;
+  id _observers;  // weak
 }
 
 - (instancetype)initWithObserver:(CRBProtocolObservers*)observers {
   self = [super init];
   if (self) {
     _observers = observers;
   }
   return self;
 }
 
@@ skipping 12 matching lines @@
 
 - (void)nestedMutateByAddingObserver:(id<TestObserver>)observer {
   [_observers mutateByAddingObserver:observer];
 }
 
 - (void)nestedMutateByRemovingObserver:(id<TestObserver>)observer {
   [_observers mutateByRemovingObserver:observer];
 }
 
 @end