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

cc/picture.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_PICTURE_H_
 #define CC_PICTURE_H_
 
 #include <list>
 
 #include "base/basictypes.h"
@@ skipping 29 matching lines @@
   bool HasRecording() const { return picture_.get(); }
 
   // Raster this Picture's layer_rect into the given canvas.
   // Assumes contentsScale have already been applied.
   void Raster(SkCanvas* canvas);
 
   void GatherPixelRefs(const gfx::Rect& rect,
                        std::list<skia::LazyPixelRef*>&);
 
 private:
-  Picture(gfx::Rect layer_rect);
+  explicit Picture(gfx::Rect layer_rect);
   // This constructor assumes SkPicture is already ref'd and transfers
   // ownership to this picture.
   Picture(const skia::RefPtr<SkPicture>&,
           gfx::Rect layer_rect,
           gfx::Rect opaque_rect);
   ~Picture();
 
   gfx::Rect layer_rect_;
   gfx::Rect opaque_rect_;
   skia::RefPtr<SkPicture> picture_;
 
   friend class base::RefCountedThreadSafe<Picture>;
   DISALLOW_COPY_AND_ASSIGN(Picture);
 };
 
 }  // namespace cc
 
 #endif  // CC_PICTURE_H_