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

chrome/browser/component_updater/test/component_updater_service_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 "chrome/browser/component_updater/component_updater_service.h"
 
 #include "base/compiler_specific.h"
 #include "base/file_path.h"
 #include "base/file_util.h"
 #include "base/memory/scoped_vector.h"
@@ skipping 64 matching lines @@
 
   // Set how many update checks are called, the default value is just once.
   void SetLoopCount(int times) { times_ = times; }
 
  private:
   int times_;
 };
 
 class TestInstaller : public ComponentInstaller {
  public :
-  explicit TestInstaller()
+  TestInstaller()
       : error_(0), install_count_(0) {
   }
 
   virtual void OnUpdateError(int error) OVERRIDE {
     EXPECT_NE(0, error);
     error_ = error;
   }
 
   virtual bool Install(base::DictionaryValue* manifest,
                        const FilePath& unpack_path) OVERRIDE {
@@ skipping 301 matching lines @@
   test_configurator()->SetLoopCount(1);
   component_updater()->Start();
   message_loop.Run();
 
   EXPECT_EQ(1, interceptor.GetHitCount());
   EXPECT_EQ(0, static_cast<TestInstaller*>(com.installer)->error());
   EXPECT_EQ(0, static_cast<TestInstaller*>(com.installer)->install_count());
 
   component_updater()->Stop();
 }