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

cc/region.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 CC_REGION_H_
 #define CC_REGION_H_
 
 #include <string>
 
 #include "base/logging.h"
@@ skipping 38 matching lines @@
 
   gfx::Rect bounds() const {
     return gfx::SkIRectToRect(skregion_.getBounds());
   }
 
   std::string ToString() const;
 
   class CC_EXPORT Iterator {
    public:
     Iterator();
-    Iterator(const Region& region);
+    explicit Iterator(const Region& region);
     ~Iterator();
 
     gfx::Rect rect() const {
       return gfx::SkIRectToRect(it_.rect());
     }
 
     void next() {
       it_.next();
     }
 
@@ skipping 49 matching lines @@
 
 inline Region UnionRegions(const Region& a, gfx::Rect b) {
   Region result = a;
   result.Union(b);
   return result;
 }
 
 }  // namespace cc
 
 #endif  // CC_REGION_H_