Revert r78134+r78136

ui/base/clipboard/clipboard_mac.mm

Index: ui/base/clipboard/clipboard_mac.mm
diff --git a/ui/base/clipboard/clipboard_mac.mm b/ui/base/clipboard/clipboard_mac.mm
index 2761ebaf1a20cf65314fde855fbec40d595467bd..89ad97d1f5b1833cb6bf4de6e41bfa735739d627 100644
--- a/ui/base/clipboard/clipboard_mac.mm
+++ b/ui/base/clipboard/clipboard_mac.mm
@@ -222,14 +222,6 @@ void Clipboard::ReadHTML(Clipboard::Buffer buffer, string16* markup,
     src_url->clear();
 }
 
-void Clipboard::ReadImage(Buffer buffer, std::string* data) const {
-  DCHECK_EQ(buffer, BUFFER_STANDARD);
-  if (!data) {
-    NOTREACHED();
-    return;
-  }
-}
-
 void Clipboard::ReadBookmark(string16* title, std::string* url) const {
   NSPasteboard* pb = GetPasteboard();