Revert r150228 "Add support for PNG representation in gfx::Image"

ui/gfx/image/image_unittest_util_mac.mm

Index: ui/gfx/image/image_unittest_util_mac.mm
diff --git a/ui/gfx/image/image_unittest_util_mac.mm b/ui/gfx/image/image_unittest_util_mac.mm
deleted file mode 100644
index e0c70639530c05b9a12dc9345b37179088288ea0..0000000000000000000000000000000000000000
--- a/ui/gfx/image/image_unittest_util_mac.mm
+++ /dev/null
@@ -1,21 +0,0 @@
-// 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.
-
-#import <AppKit/AppKit.h>
-
-#include "skia/ext/skia_utils_mac.h"
-#include "ui/gfx/image/image_unittest_util.h"
-
-namespace gfx {
-namespace test {
-
-SkColor GetPlatformImageColor(PlatformImage image) {
-  [image lockFocus];
-  NSColor* color = NSReadPixel(NSMakePoint(10, 10));
-  [image unlockFocus];
-  return NSDeviceColorToSkColor(color);
-}
-
-}  // namespace test
-}  // namespace gfx