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

cc/tree_synchronizer_unittest.cc

 // Copyright 2011 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 "cc/tree_synchronizer.h"
 
 #include <algorithm>
 
 #include "cc/layer.h"
 #include "cc/layer_animation_controller.h"
@@ skipping 46 matching lines @@
 
     virtual void pushPropertiesTo(LayerImpl* layerImpl) OVERRIDE
     {
         Layer::pushPropertiesTo(layerImpl);
 
         MockLayerImpl* mockLayerImpl = static_cast<MockLayerImpl*>(layerImpl);
         mockLayerImpl->setLayerImplDestructionList(m_layerImplDestructionList);
     }
 
 private:
-    MockLayer(std::vector<int>* layerImplDestructionList)
+    explicit MockLayer(std::vector<int>* layerImplDestructionList)
         : Layer()
         , m_layerImplDestructionList(layerImplDestructionList)
     {
     }
     virtual ~MockLayer() { }
 
     std::vector<int>* m_layerImplDestructionList;
 };
 
 class FakeLayerAnimationController : public LayerAnimationController {
@@ skipping 298 matching lines @@
     EXPECT_FALSE(static_cast<FakeLayerAnimationController*>(layerTreeRoot->layerAnimationController())->synchronizedAnimations());
 
     scoped_ptr<LayerImpl> layerImplTreeRoot = TreeSynchronizer::synchronizeTrees(layerTreeRoot.get(), scoped_ptr<LayerImpl>(), m_hostImpl.activeTree());
     layerImplTreeRoot = TreeSynchronizer::synchronizeTrees(layerTreeRoot.get(), layerImplTreeRoot.Pass(), m_hostImpl.activeTree());
 
     EXPECT_TRUE(static_cast<FakeLayerAnimationController*>(layerTreeRoot->layerAnimationController())->synchronizedAnimations());
 }
 
 }  // namespace
 }  // namespace cc