[MD settings] disable clear browsing data while it is running

chrome/browser/browsing_data/browsing_data_remover.h

Index: chrome/browser/browsing_data/browsing_data_remover.h
diff --git a/chrome/browser/browsing_data/browsing_data_remover.h b/chrome/browser/browsing_data/browsing_data_remover.h
index 9e12be054b20b9017f3bf3c858329eb5e34f4cd3..d208d10cfa94e362ed4fce88f3f7bd46d1865473 100644
--- a/chrome/browser/browsing_data/browsing_data_remover.h
+++ b/chrome/browser/browsing_data/browsing_data_remover.h
@@ -175,10 +175,16 @@ class BrowsingDataRemover : public KeyedService
     base::Time end;
   };
 
-  // Observer is notified when the removal is done. Done means keywords have
-  // been deleted, cache cleared and all other tasks scheduled.
+  // Observer is notified when the removal is active and when it's done.
   class Observer {
    public:
+    // Whether removal is active. Note that not having an active removal is not
+    // same as completing a removal. That is why the removing status is separate
+    // from the done message.
+    virtual void OnBrowsingDataRemoving(bool is_removing) {}
+
+    // Done means keywords have been deleted, cache cleared and all other
+    // removal tasks are scheduled.
     virtual void OnBrowsingDataRemoverDone() = 0;
 
    protected: