Make WeakContainer safe when weak_nsobject.h is included from ARC code.

base/ios/weak_nsobject.mm

 // Copyright 2013 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 "base/ios/weak_nsobject.h"
 
 #include "base/mac/scoped_nsautorelease_pool.h"
 #include "base/mac/scoped_nsobject.h"
 
 namespace {
 // The key needed by objc_setAssociatedObject.
 char sentinelObserverKey_;
 }
 
+namespace base {
+
+WeakContainer::WeakContainer(id object) : object_(object) {}
+
+WeakContainer::~WeakContainer() {}
+
+}  // namespace base
+
 @interface CRBWeakNSProtocolSentinel ()
 // Container to notify on dealloc.
 @property(readonly, assign) scoped_refptr<base::WeakContainer> container;
 // Designed initializer.
 - (id)initWithContainer:(scoped_refptr<base::WeakContainer>)container;
 @end
 
 @implementation CRBWeakNSProtocolSentinel
 
 @synthesize container = container_;
@@ skipping 27 matching lines @@
     container_ = container;
   return self;
 }
 
 - (void)dealloc {
   self.container->nullify();
   [super dealloc];
 }
 
 @end