Gtk3 ui: Add libgtk3ui as a separate build component

chrome/browser/ui/libgtkui/skia_utils_gtk2.cc

 // 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.
 
-#include "chrome/browser/ui/libgtk2ui/skia_utils_gtk2.h"
+#include "chrome/browser/ui/libgtkui/skia_utils_gtk2.h"
 
 #include <gdk/gdk.h>
 
 #include "base/logging.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "third_party/skia/include/core/SkUnPreMultiply.h"
 
-namespace libgtk2ui {
+namespace libgtkui {
 
 // GDK_COLOR_RGB multiplies by 257 (= 0x10001) to distribute the bits evenly
 // See: http://www.mindcontrol.org/~hplus/graphics/expand-bits.html
 // To get back, we can just right shift by eight
 // (or, formulated differently, i == (i*257)/256 for all i < 256).
 
 SkColor GdkColorToSkColor(GdkColor color) {
   return SkColorSetRGB(color.red >> 8, color.green >> 8, color.blue >> 8);
 }
 
@@ skipping 99 matching lines @@
         divided[i + 2] = SkColorGetB(pixel);
         divided[i + 3] = alpha;
       }
       i += kBytesPerPixel;
     }
   }
 
   return pixbuf;
 }
 
-}  // namespace libgtk2ui
+}  // namespace libgtkui