Add new extension APIs related to animation policy.

chrome/browser/accessibility/accessibility_notifier.h

+// Copyright 2015 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 CHROME_BROWSER_ACCESSIBILITY_ACCESSIBILITY_NOTIFIER_H_
+#define CHROME_BROWSER_ACCESSIBILITY_ACCESSIBILITY_NOTIFIER_H_
+
+#include "base/basictypes.h"
+#include "base/compiler_specific.h"
+#include "base/prefs/pref_change_registrar.h"
+#include "components/keyed_service/core/keyed_service.h"
+#include "content/public/browser/notification_observer.h"
+#include "content/public/browser/notification_registrar.h"
+
+class Profile;
+
+// Observes a set of prefs in the login profile. If any of the prefs
+// related to Accessibility is updated, the status is reported to callback.
+class AccessibilityNotifier : public KeyedService {
+ public:
+  explicit AccessibilityNotifier(Profile* profile);
+  ~AccessibilityNotifier() override;
+
+  // KeyedService:
+  void Shutdown() override;
+
+ private:
+  enum AnimationPolicy {

[Lei Zhang, 2015/01/28 19:38:43]

Can't you just reuse content::ImageAnimationPolicy?

+    ANIMATION_POLICY_ALLOWED,
+    ANIMATION_POLICY_ANIMATION_ONCE,
+    ANIMATION_POLICY_NO_ANIMATION
+  };
+
+  void UpdateAnimationPolicyFromPref();
+  void SetProfile(Profile*);

[Lei Zhang, 2015/01/28 19:38:43]

nit: we generally include the parameter name

+
+  // Profile which has the current a11y context.
+  Profile* profile_;
+  AnimationPolicy animation_policy_;
+  content::NotificationRegistrar notification_registrar_;
+  scoped_ptr<PrefChangeRegistrar> pref_change_registrar_;
+
+  DISALLOW_COPY_AND_ASSIGN(AccessibilityNotifier);
+};
+#endif  // CHROME_BROWSER_ACCESSIBILITY_ACCESSIBILITY_NOTIFIER_H_