[subresource_filter] Add observer interface for page activation

components/subresource_filter/content/browser/subresource_filter_observer_manager.h

Index: components/subresource_filter/content/browser/subresource_filter_observer_manager.h
diff --git a/components/subresource_filter/content/browser/subresource_filter_observer_manager.h b/components/subresource_filter/content/browser/subresource_filter_observer_manager.h
new file mode 100644
index 0000000000000000000000000000000000000000..489fb2143068ce776ced2e73f73af6e16e0303ea
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+++ b/components/subresource_filter/content/browser/subresource_filter_observer_manager.h
@@ -0,0 +1,49 @@
+// Copyright 2017 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 COMPONENTS_SUBRESOURCE_FILTER_CONTENT_BROWSER_SUBRESOURCE_FILTER_OBSERVER_MANAGER_H_
+#define COMPONENTS_SUBRESOURCE_FILTER_CONTENT_BROWSER_SUBRESOURCE_FILTER_OBSERVER_MANAGER_H_
+
+#include "base/macros.h"
+#include "base/observer_list.h"
+#include "components/subresource_filter/content/browser/subresource_filter_observer.h"
+#include "components/subresource_filter/core/common/activation_decision.h"
+#include "content/public/browser/web_contents_user_data.h"
+
+namespace content {
+class NavigationHandle;
+class WebContents;
+}  // namespace content
+
+namespace subresource_filter {
+
+struct ActivationState;
+
+// Manages retaining the list of SubresourceFilterObservers and notifying them
+// of various filtering events. Scoped to the lifetime of a WebContents.
+class SubresourceFilterObserverManager
+    : public content::WebContentsUserData<SubresourceFilterObserverManager> {
+ public:
+  explicit SubresourceFilterObserverManager(content::WebContents* web_contents);
+  ~SubresourceFilterObserverManager() override;
+
+  void AddObserver(SubresourceFilterObserver* observer);
+  void RemoveObserver(SubresourceFilterObserver* observer);
+
+  // Will be called at the latest in the WillProcessResponse stage from a
+  // NavigationThrottle that was registered before the throttle manager's
+  // throttles created in MaybeAppendNavigationThrottles().
+  void NotifyPageActivationComputed(
+      content::NavigationHandle* navigation_handle,
+      ActivationDecision activation_decision,
+      const ActivationState& activation_state);
+
+ private:
+  base::ObserverList<SubresourceFilterObserver> observers_;
+  DISALLOW_COPY_AND_ASSIGN(SubresourceFilterObserverManager);
+};
+
+}  // namespace subresource_filter
+
+#endif  // COMPONENTS_SUBRESOURCE_FILTER_CONTENT_BROWSER_SUBRESOURCE_FILTER_OBSERVER_MANAGER_H_