Fix NSPasteboard leaks.

ui/base/clipboard/clipboard_util_mac.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.
 
 #include "ui/base/clipboard/clipboard_util_mac.h"
 
 #include "base/mac/foundation_util.h"
 #include "base/mac/scoped_cftyperef.h"
 
 namespace {
 NSString* const kWebURLsWithTitlesPboardType = @"WebURLsWithTitlesPboardType";
 NSString* const kCorePasteboardFlavorType_url =
     @"CorePasteboardFlavorType 0x75726C20";  // 'url '  url
 NSString* const kCorePasteboardFlavorType_urln =
     @"CorePasteboardFlavorType 0x75726C6E";  // 'urln'  title
 
 // It's much more convenient to return an NSString than a
 // base::ScopedCFTypeRef<CFStringRef>, since the methods on NSPasteboardItem
 // require an NSString*.
 NSString* UTIFromPboardType(NSString* type) {
   return [base::mac::CFToNSCast(UTTypeCreatePreferredIdentifierForTag(
       kUTTagClassNSPboardType, base::mac::NSToCFCast(type), kUTTypeData))
       autorelease];
 }
 }  // namespace
 
 namespace ui {
 
+UniquePasteboard::UniquePasteboard()
+    : pasteboard_([[NSPasteboard pasteboardWithUniqueName] retain]) {}
+
+UniquePasteboard::~UniquePasteboard() {
+  [pasteboard_ releaseGlobally];

[Avi (use Gerrit), 2016/04/01 18:21:01]

OMG

Yes, the docs imply this, but this isn't at all obvious.

o_O

+}
+
 // static
 base::scoped_nsobject<NSPasteboardItem> ClipboardUtil::PasteboardItemFromUrl(
     NSString* urlString,
     NSString* title) {
   DCHECK(urlString);
   if (!title)
     title = urlString;
 
   base::scoped_nsobject<NSPasteboardItem> item([[NSPasteboardItem alloc] init]);
 
@@ skipping 25 matching lines @@
 
   [item setData:[urlString dataUsingEncoding:NSUTF8StringEncoding]
         forType:UTIFromPboardType(kCorePasteboardFlavorType_url)];
 
   [item setData:[title dataUsingEncoding:NSUTF8StringEncoding]
         forType:UTIFromPboardType(kCorePasteboardFlavorType_urln)];
   return item;
 }
 
 }  // namespace ui