Upstream various ios/web utilities and helpers

ios/web/weak_nsobject_counter.h

Index: ios/web/weak_nsobject_counter.h
diff --git a/ios/web/weak_nsobject_counter.h b/ios/web/weak_nsobject_counter.h
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+// 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.
+
+#ifndef IOS_WEB_WEAK_NSOBJECT_COUNTER_H_
+#define IOS_WEB_WEAK_NSOBJECT_COUNTER_H_
+
+#import <Foundation/Foundation.h>
+
+#include "base/memory/linked_ptr.h"
+#include "base/threading/non_thread_safe.h"
+
+namespace web {
+
+// WeakNSObjectCounter is a class to maintain a counter of all the objects
+// that are added using |Insert| that are alive.
+// This class is not thread safe and objects must be destroyed and created on
+// the same thread.
+// TODO(stuartmorgan): Remove this once ARC is supported.
+class WeakNSObjectCounter : public base::NonThreadSafe {
+ public:
+  WeakNSObjectCounter();
+  ~WeakNSObjectCounter();
+  // Inserts an object. |object| cannot be nil.
+  void Insert(id object);
+  // Returns the count of all active objects that have been inserted.
+  NSUInteger Size() const;
+ private:
+  // The object that maintains the number of active items.
+  linked_ptr<NSUInteger> counter_;
+};
+
+}  // namespace web
+
+#endif  // IOS_WEB_WEAK_NSOBJECT_COUNTER_H_