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

ui/gfx/image/image.cc

Index: ui/gfx/image/image.cc
diff --git a/ui/gfx/image/image.cc b/ui/gfx/image/image.cc
index b09b66f571d1a050cd5fcfa3b66a3600bdca789c..18bf81d5ce32f8d65f77943ac291dc27a4470444 100644
--- a/ui/gfx/image/image.cc
+++ b/ui/gfx/image/image.cc
@@ -246,7 +246,7 @@ class ImageRepPNG : public ImageRep {
   ImageRepPNG() : ImageRep(Image::kImageRepPNG) {
   }
 
-  ImageRepPNG(const std::vector<ImagePNGRep>& image_png_reps)
+  explicit ImageRepPNG(const std::vector<ImagePNGRep>& image_png_reps)
       : ImageRep(Image::kImageRepPNG),
         image_png_reps_(image_png_reps) {
   }
@@ -377,7 +377,7 @@ class ImageRepCocoa : public ImageRep {
 // ImageReps. This way, the Image can be cheaply copied.
 class ImageStorage : public base::RefCounted<ImageStorage> {
  public:
-  ImageStorage(gfx::Image::RepresentationType default_type)
+  explicit ImageStorage(gfx::Image::RepresentationType default_type)
       : default_representation_type_(default_type),
         representations_deleter_(&representations_) {
   }