mac: Add tests for reading images from NSPasteboard.

ui/base/clipboard/clipboard_mac.h

 // Copyright 2014 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.
 
 #ifndef UI_BASE_CLIPBOARD_CLIPBOARD_MAC_H_
 #define UI_BASE_CLIPBOARD_CLIPBOARD_MAC_H_
 
 #include <stddef.h>
 #include <stdint.h>
 
+#include "base/gtest_prod_util.h"
 #include "base/macros.h"
 #include "ui/base/clipboard/clipboard.h"
 
+@class NSPasteboard;
+
 namespace ui {
 
 class ClipboardMac : public Clipboard {
  private:
+  FRIEND_TEST_ALL_PREFIXES(ClipboardMacTest, ReadImageRetina);
+  FRIEND_TEST_ALL_PREFIXES(ClipboardMacTest, ReadImageNonRetina);
   friend class Clipboard;
 
   ClipboardMac();
   ~ClipboardMac() override;
 
   // Clipboard overrides:
   uint64_t GetSequenceNumber(ClipboardType type) const override;
   bool IsFormatAvailable(const FormatType& format,
                          ClipboardType type) const override;
   void Clear(ClipboardType type) override;
   void ReadAvailableTypes(ClipboardType type,
                           std::vector<base::string16>* types,
                           bool* contains_filenames) const override;
   void ReadText(ClipboardType type, base::string16* result) const override;
   void ReadAsciiText(ClipboardType type, std::string* result) const override;
   void ReadHTML(ClipboardType type,
                 base::string16* markup,
                 std::string* src_url,
                 uint32_t* fragment_start,
                 uint32_t* fragment_end) const override;
   void ReadRTF(ClipboardType type, std::string* result) const override;
+  SkBitmap ReadImage(ClipboardType type, NSPasteboard* pb) const;
   SkBitmap ReadImage(ClipboardType type) const override;
   void ReadCustomData(ClipboardType clipboard_type,
                       const base::string16& type,
                       base::string16* result) const override;
   void ReadBookmark(base::string16* title, std::string* url) const override;
   void ReadData(const FormatType& format, std::string* result) const override;
   void WriteObjects(ClipboardType type, const ObjectMap& objects) override;
   void WriteText(const char* text_data, size_t text_len) override;
   void WriteHTML(const char* markup_data,
                  size_t markup_len,
                  const char* url_data,
                  size_t url_len) override;
   void WriteRTF(const char* rtf_data, size_t data_len) override;
   void WriteBookmark(const char* title_data,
                      size_t title_len,
                      const char* url_data,
                      size_t url_len) override;
   void WriteWebSmartPaste() override;
   void WriteBitmap(const SkBitmap& bitmap) override;
   void WriteData(const FormatType& format,
                  const char* data_data,
                  size_t data_len) override;
 
   DISALLOW_COPY_AND_ASSIGN(ClipboardMac);
 };
 
 }  // namespace ui
 
 #endif  // UI_BASE_CLIPBOARD_CLIPBOARD_MAC_H_