Upstream Chrome on iOS source code [8/11].

ios/chrome/browser/ui/settings/utils/pref_backed_boolean.mm

+// Copyright 2016 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/browser/ui/settings/utils/pref_backed_boolean.h"
+
+#include "base/bind.h"
+#include "components/prefs/pref_member.h"
+#include "components/prefs/pref_service.h"
+
+namespace {
+
+// Adaptor function to allow invoking onChange as a base::Closure.
+void OnChange(id<ObservableBoolean> object) {
+  [object.observer booleanDidChange:object];
+}
+
+}  // namespace
+
+@implementation PrefBackedBoolean {
+  BooleanPrefMember _pref;
+}
+
+@synthesize observer = _observer;
+
+- (id)initWithPrefService:(PrefService*)prefs prefName:(const char*)prefName {
+  self = [super init];
+  if (self) {
+    // Create a base::Closure that calls onChange.
+    // Bind expects a refcounted object but allows us to pass a raw pointer
+    // with Unretained.  Since the closure will be deleted when |_pref| is
+    // deleted, which happens when |self| is deleted, we know |self| will still
+    // be valid when the closure is invoked.
+    base::Closure onChangeClosure =
+        base::Bind(&OnChange, base::Unretained(self));
+    _pref.Init(prefName, prefs, onChangeClosure);
+  }
+  return self;
+}
+
+- (BOOL)value {
+  return _pref.GetValue();
+}
+
+- (void)setValue:(BOOL)value {
+  _pref.SetValue(value == YES);
+}
+
+@end