Add missing (and remove superfluous) 'explicit' from constructors.

chrome/browser/history/in_memory_url_index.h

 // Copyright (c) 2012 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_HISTORY_IN_MEMORY_URL_INDEX_H_
 #define CHROME_BROWSER_HISTORY_IN_MEMORY_URL_INDEX_H_
 
 #include <functional>
 #include <map>
 #include <set>
@@ skipping 132 matching lines @@
   friend class InMemoryURLIndexTest;
   friend class InMemoryURLIndexCacheTest;
   FRIEND_TEST_ALL_PREFIXES(LimitedInMemoryURLIndexTest, Initialization);
 
   // Creating one of me without a history path is not allowed (tests excepted).
   InMemoryURLIndex();
 
   // HistoryDBTask used to rebuild our private data from the history database.
   class RebuildPrivateDataFromHistoryDBTask : public HistoryDBTask {
    public:
-    explicit RebuildPrivateDataFromHistoryDBTask(
+    RebuildPrivateDataFromHistoryDBTask(
         InMemoryURLIndex* index,
         const std::string& languages,
         const std::set<std::string>& scheme_whitelist);
 
     virtual bool RunOnDBThread(HistoryBackend* backend,
                                history::HistoryDatabase* db) OVERRIDE;
     virtual void DoneRunOnMainThread() OVERRIDE;
 
    private:
     virtual ~RebuildPrivateDataFromHistoryDBTask();
@@ skipping 120 matching lines @@
   // TODO(mrossetti): Eliminate once the transition to SQLite has been done.
   // http://crbug.com/83659
   bool needs_to_be_cached_;
 
   DISALLOW_COPY_AND_ASSIGN(InMemoryURLIndex);
 };
 
 }  // namespace history
 
 #endif  // CHROME_BROWSER_HISTORY_IN_MEMORY_URL_INDEX_H_