mac: Don't lose pixels when copying a retina image from the clipboard.

ui/base/clipboard/clipboard_mac_unittest.mm

 // Copyright 2016 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 "ui/base/clipboard/clipboard_mac.h"
 
 #include "base/mac/scoped_cftyperef.h"
 #include "base/mac/scoped_nsobject.h"
 #include "base/memory/free_deleter.h"
 #include "base/memory/ref_counted.h"
@@ skipping 35 matching lines @@
   int32_t height = 101;
   scoped_refptr<ui::UniquePasteboard> pasteboard = new ui::UniquePasteboard;
   base::scoped_nsobject<NSImage> image = CreateImage(width, height, true);
   [pasteboard->get() writeObjects:@[ image.get() ]];
 
   ui::Clipboard* clipboard = ui::Clipboard::GetForCurrentThread();
   ui::ClipboardMac* clipboard_mac = static_cast<ui::ClipboardMac*>(clipboard);
 
   SkBitmap bitmap = clipboard_mac->ReadImage(ui::CLIPBOARD_TYPE_COPY_PASTE,
                                              pasteboard->get());
-  EXPECT_EQ(width, bitmap.width());
-  EXPECT_EQ(height, bitmap.height());
+  EXPECT_EQ(2 * width, bitmap.width());
+  EXPECT_EQ(2 * height, bitmap.height());
 }
 
 TEST_F(ClipboardMacTest, ReadImageNonRetina) {
   int32_t width = 99;
   int32_t height = 101;
   scoped_refptr<ui::UniquePasteboard> pasteboard = new ui::UniquePasteboard;
   base::scoped_nsobject<NSImage> image = CreateImage(width, height, false);
   [pasteboard->get() writeObjects:@[ image.get() ]];
 
   ui::Clipboard* clipboard = ui::Clipboard::GetForCurrentThread();
   ui::ClipboardMac* clipboard_mac = static_cast<ui::ClipboardMac*>(clipboard);
 
   SkBitmap bitmap = clipboard_mac->ReadImage(ui::CLIPBOARD_TYPE_COPY_PASTE,
                                              pasteboard->get());
   EXPECT_EQ(width, bitmap.width());
   EXPECT_EQ(height, bitmap.height());
 }
 
 }  // namespace ui