image-skia: Remove implicit conversion to SkBitmap on linux and chromeos.

ui/gfx/image/image_skia_unittest.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 "ui/gfx/image/image_skia.h"
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/skia/include/core/SkBitmap.h"
 #include "ui/base/layout.h"
 #include "ui/gfx/image/image_skia_rep.h"
@@ skipping 170 matching lines @@
   empty_image.RemoveRepresentation(ui::SCALE_FACTOR_100P);
 
   // Check that ImageSkia::bitmap() still returns a valid SkBitmap pointer for
   // the image and all its copies.
   const SkBitmap* bitmap = empty_image_copy.bitmap();
   ASSERT_NE(static_cast<SkBitmap*>(NULL), bitmap);
   EXPECT_TRUE(bitmap->isNull());
   EXPECT_TRUE(bitmap->empty());
 }
 
+#if defined(OS_MACOSX) || defined(OS_WIN)
 TEST(ImageSkiaTest, OperatorBitmapFromSource) {
   ImageSkia image_skia(new DynamicSource(Size(100, 200)), Size(100, 200));
   // ImageSkia should use the source to create the bitmap.
   const SkBitmap& bitmap = image_skia;
   ASSERT_NE(static_cast<SkBitmap*>(NULL), &bitmap);
   EXPECT_FALSE(bitmap.isNull());
 }
+#endif
 
 TEST(ImageSkiaTest, BackedBySameObjectAs) {
   // Null images should all be backed by the same object (NULL).
   ImageSkia image;
   ImageSkia unrelated;
   EXPECT_TRUE(image.BackedBySameObjectAs(unrelated));
 
   image.AddRepresentation(gfx::ImageSkiaRep(gfx::Size(10, 10),
                                             ui::SCALE_FACTOR_100P));
   ImageSkia copy = image;
   copy.AddRepresentation(gfx::ImageSkiaRep(gfx::Size(10, 10),
                                            ui::SCALE_FACTOR_200P));
   unrelated.AddRepresentation(gfx::ImageSkiaRep(gfx::Size(10, 10),
                                                 ui::SCALE_FACTOR_100P));
   EXPECT_TRUE(image.BackedBySameObjectAs(copy));
   EXPECT_FALSE(image.BackedBySameObjectAs(unrelated));
   EXPECT_FALSE(copy.BackedBySameObjectAs(unrelated));
 }
 
 }  // namespace gfx