Make BrowsingDataHandler observe WebHistoryService deletions

components/history/core/browser/web_history_service.h

Index: components/history/core/browser/web_history_service.h
diff --git a/components/history/core/browser/web_history_service.h b/components/history/core/browser/web_history_service.h
index 0b6c08bdc86839c3ef68300382d6a3bcb7c1ac5a..51d9db0d512e20890ef9ce89c5df52c2fc4e7106 100644
--- a/components/history/core/browser/web_history_service.h
+++ b/components/history/core/browser/web_history_service.h
@@ -14,6 +14,7 @@
 #include "base/macros.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/weak_ptr.h"
+#include "base/observer_list.h"
 #include "components/history/core/browser/history_types.h"
 #include "components/keyed_service/core/keyed_service.h"
 
@@ -34,11 +35,23 @@ class SigninManagerBase;
 
 namespace history {
 
+class HistoryServiceObserver;
+
 // Provides an API for querying Google servers for a signed-in user's
 // synced history visits. It is roughly analogous to HistoryService, and
 // supports a similar API.
 class WebHistoryService : public KeyedService {
  public:
+  // Observes WebHistoryService actions. Currently only history expiration
+  // is supported.
+  // TODO(msramek): Consider defining ObservableHistoryService as a common
+  // abstract ancestor for HistoryService and WebHistoryService. Then, we could
+  // change the signatures of HistoryServiceObserver to use it for both classes.
+  class Observer {
+   public:
+    virtual void OnWebHistoryDeleted() = 0;
+  };
+
   // Handles all the work of making an API request. This class encapsulates
   // the entire state of the request. When an instance is destroyed, all
   // aspects of the request are cancelled.
@@ -95,6 +108,9 @@ class WebHistoryService : public KeyedService {
       const scoped_refptr<net::URLRequestContextGetter>& request_context);
   ~WebHistoryService() override;
 
+  void AddObserver(Observer* observer);
+  void RemoveObserver(Observer* observer);
+
   // Searches synced history for visits matching |text_query|. The timeframe to
   // search, along with other options, is specified in |options|. If
   // |text_query| is empty, all visits in the timeframe will be returned.
@@ -219,6 +235,9 @@ class WebHistoryService : public KeyedService {
   // complete by profile shutdown.
   std::set<Request*> pending_other_forms_of_browsing_history_requests_;
 
+  // Observers.
+  base::ObserverList<Observer, true> observer_list_;
+
   base::WeakPtrFactory<WebHistoryService> weak_ptr_factory_;
 
   DISALLOW_COPY_AND_ASSIGN(WebHistoryService);