[Sync] Fix namespaces for the sync_sessions component.

components/sync_sessions/revisit/bookmarks_page_revisit_observer.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 COMPONENTS_SYNC_SESSIONS_REVISIT_BOOKMARKS_PAGE_REVISIT_OBSERVER_H_
 #define COMPONENTS_SYNC_SESSIONS_REVISIT_BOOKMARKS_PAGE_REVISIT_OBSERVER_H_
 
 #include <memory>
 #include <vector>
 
@@ skipping 19 matching lines @@
   virtual ~BookmarksByUrlProvider() {}
 };
 
 // Responds to OnPageVisit events by looking for bookmarks with matching URLs,
 // and emits metrics about the results. If multiple bookmarks match, the most
 // recently created one is used. Currently there isn't enough information to
 // determine modificatoin times or remote vs local. This observer does all
 // processing in task/thread, which is okay since it only accesses values in
 // memory. Potential slow downs could occur when it fails to get bookmarks lock
 // and when the number of matching Bookmarks for a single URL is very large.
-class BookmarksPageRevisitObserver : public sync_sessions::PageVisitObserver {
+class BookmarksPageRevisitObserver : public PageVisitObserver {
  public:
   explicit BookmarksPageRevisitObserver(
       std::unique_ptr<BookmarksByUrlProvider> provider);
   ~BookmarksPageRevisitObserver() override;
   void OnPageVisit(const GURL& url, const TransitionType transition) override;
 
  private:
   std::unique_ptr<BookmarksByUrlProvider> provider_;
   DISALLOW_COPY_AND_ASSIGN(BookmarksPageRevisitObserver);
 };
 
 }  // namespace sync_sessions
 
 #endif  // COMPONENTS_SYNC_SESSIONS_REVISIT_BOOKMARKS_PAGE_REVISIT_OBSERVER_H_