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

ui/base/dragdrop/os_exchange_data_provider_mac.mm

Index: ui/base/dragdrop/os_exchange_data_provider_mac.mm
diff --git a/ui/base/dragdrop/os_exchange_data_provider_mac.mm b/ui/base/dragdrop/os_exchange_data_provider_mac.mm
index 9f9fa915ca48465435f7d41c69db236e602c0e05..11b0a495bb12312609aef9ad8992d20b8ca1724c 100644
--- a/ui/base/dragdrop/os_exchange_data_provider_mac.mm
+++ b/ui/base/dragdrop/os_exchange_data_provider_mac.mm
@@ -29,8 +29,10 @@ OSExchangeDataProviderMac::OSExchangeDataProviderMac(
 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() {
@@ -199,7 +201,8 @@ OSExchangeDataProviderMac::CreateDataFromPasteboard(NSPasteboard* pasteboard) {
   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
@@ -212,12 +215,4 @@ NSArray* OSExchangeDataProviderMac::SupportedPasteboardTypes() {
   ];
 }
 
-///////////////////////////////////////////////////////////////////////////////
-// OSExchangeData, public:
-
-// static
-OSExchangeData::Provider* OSExchangeData::CreateProvider() {
-  return new OSExchangeDataProviderMac;
-}
-
 }  // namespace ui