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

content/browser/download/download_manager_impl_unittest.cc

 // 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.
 
 #include <set>
 #include <string>
 
 #include "base/bind.h"
 #include "base/file_util.h"
 #include "base/files/scoped_temp_dir.h"
@@ skipping 46 matching lines @@
 // Matches a DownloadCreateInfo* that points to the same object as |info| and
 // has a |default_download_directory| that matches |download_directory|.
 MATCHER_P2(DownloadCreateInfoWithDefaultPath, info, download_directory, "") {
   return arg == info &&
       arg->default_download_directory == download_directory;
 }
 
 class MockDownloadItemImpl : public DownloadItemImpl {
  public:
   // Use history constructor for minimal base object.
-  MockDownloadItemImpl(DownloadItemImplDelegate* delegate)
+  explicit MockDownloadItemImpl(DownloadItemImplDelegate* delegate)
       : DownloadItemImpl(
           delegate,
           content::DownloadId(),
           FilePath(),
           GURL(),
           GURL(),
           base::Time(),
           base::Time(),
           0,
           0,
@@ skipping 566 matching lines @@
   callback_called_ = false;
   DetermineDownloadTarget(&item);
   EXPECT_TRUE(callback_called_);
   EXPECT_EQ(path, target_path_);
   EXPECT_EQ(DownloadItem::TARGET_DISPOSITION_OVERWRITE, target_disposition_);
   EXPECT_EQ(DOWNLOAD_DANGER_TYPE_NOT_DANGEROUS, danger_type_);
   EXPECT_EQ(path, intermediate_path_);
 }
 
 }  // namespace content