Allow OSExchangeData::Provider to be overridden at run time.

ui/base/dragdrop/os_exchange_data_provider_mac.mm

 // 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.
 
 #include "ui/base/dragdrop/os_exchange_data_provider_mac.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/logging.h"
 #include "base/memory/ptr_util.h"
@@ skipping 11 matching lines @@
 OSExchangeDataProviderMac::OSExchangeDataProviderMac()
     : pasteboard_(new ui::UniquePasteboard) {}
 
 OSExchangeDataProviderMac::OSExchangeDataProviderMac(
     scoped_refptr<ui::UniquePasteboard> pb)
     : pasteboard_(pb) {}
 
 OSExchangeDataProviderMac::~OSExchangeDataProviderMac() {
 }
 
-OSExchangeData::Provider* OSExchangeDataProviderMac::Clone() const {
-  return new OSExchangeDataProviderMac(pasteboard_);
+std::unique_ptr<OSExchangeData::Provider>
+OSExchangeDataProviderMac::Clone() const {
+  return std::unique_ptr<OSExchangeData::Provider>(
+      new OSExchangeDataProviderMac(pasteboard_));
 }
 
 void OSExchangeDataProviderMac::MarkOriginatedFromRenderer() {
   NOTIMPLEMENTED();
 }
 
 bool OSExchangeDataProviderMac::DidOriginateFromRenderer() const {
   NOTIMPLEMENTED();
   return false;
 }
@@ skipping 148 matching lines @@
 }
 
 // static
 std::unique_ptr<OSExchangeData>
 OSExchangeDataProviderMac::CreateDataFromPasteboard(NSPasteboard* pasteboard) {
   OSExchangeDataProviderMac* provider = new OSExchangeDataProviderMac();
 
   for (NSPasteboardItem* item in [pasteboard pasteboardItems])
     ClipboardUtil::AddDataToPasteboard(provider->pasteboard_->get(), item);
 
-  return base::MakeUnique<OSExchangeData>(provider);
+  return base::MakeUnique<OSExchangeData>(
+      base::WrapUnique<OSExchangeData::Provider>(provider));
 }
 
 // static
 NSArray* OSExchangeDataProviderMac::SupportedPasteboardTypes() {
   return @[
     kWebCustomDataPboardType, ui::ClipboardUtil::UTIForWebURLsAndTitles(),
     NSURLPboardType, NSFilenamesPboardType, ui::kChromeDragDummyPboardType,
     NSStringPboardType, NSHTMLPboardType, NSRTFPboardType,
     NSFilenamesPboardType, ui::kWebCustomDataPboardType, NSPasteboardTypeString
   ];
 }
 
-///////////////////////////////////////////////////////////////////////////////
-// OSExchangeData, public:
-
-// static
-OSExchangeData::Provider* OSExchangeData::CreateProvider() {
-  return new OSExchangeDataProviderMac;
-}
-
 }  // namespace ui