Fix cpplint errors in cc/(animation|input|layers|trees|test)/

cc/test/fake_web_scrollbar_theme_geometry.h

 // Copyright 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 CC_TEST_FAKE_WEB_SCROLLBAR_THEME_GEOMETRY_H_
 #define CC_TEST_FAKE_WEB_SCROLLBAR_THEME_GEOMETRY_H_
 
 #include "base/memory/scoped_ptr.h"
 #include "third_party/WebKit/Source/Platform/chromium/public/WebScrollbarThemeGeometry.h"
 
@@ skipping 29 matching lines @@
   virtual WebKit::WebRect constrainTrackRectToTrackPieces(
       WebKit::WebScrollbar* scrollbar,
       const WebKit::WebRect& rect) OVERRIDE;
   virtual void splitTrack(WebKit::WebScrollbar* scrollbar,
                           const WebKit::WebRect& track,
                           WebKit::WebRect& start_track,
                           WebKit::WebRect& thumb,
                           WebKit::WebRect& end_track) OVERRIDE;
 
  protected:
-  FakeWebScrollbarThemeGeometry(bool has_thumb) : has_thumb_(has_thumb) {}
+  explicit FakeWebScrollbarThemeGeometry(bool has_thumb)
+      : has_thumb_(has_thumb) {}
   bool has_thumb_;
 };
 
 }  // namespace cc
 
 #endif  // CC_TEST_FAKE_WEB_SCROLLBAR_THEME_GEOMETRY_H_