mash: Use the new mus drag and drop API to get drag working in mash.

ui/views/mus/os_exchange_data_provider_mus.cc

Index: ui/views/mus/os_exchange_data_provider_mus.cc
diff --git a/ui/views/mus/os_exchange_data_provider_mus.cc b/ui/views/mus/os_exchange_data_provider_mus.cc
index 008ad1e659c17edbd88e347570b01b8053a26b56..7d47924848a14be964e593a97e00740c56501ecc 100644
--- a/ui/views/mus/os_exchange_data_provider_mus.cc
+++ b/ui/views/mus/os_exchange_data_provider_mus.cc
@@ -4,6 +4,11 @@
 
 #include "ui/views/mus/os_exchange_data_provider_mus.h"
 
+#include <memory>
+#include <string>
+#include <utility>
+#include <vector>
+
 #include "base/stl_util.h"
 #include "base/strings/string_split.h"
 #include "base/strings/string_util.h"
@@ -52,6 +57,9 @@ void AddString16ToVector(const base::string16& str,
 
 OSExchangeDataProviderMus::OSExchangeDataProviderMus() {}
 
+OSExchangeDataProviderMus::OSExchangeDataProviderMus(Data data)
+    : mime_data_(std::move(data)) {}
+
 OSExchangeDataProviderMus::~OSExchangeDataProviderMus() {}
 
 OSExchangeDataProviderMus::Data OSExchangeDataProviderMus::GetData() const {
@@ -251,7 +259,6 @@ bool OSExchangeDataProviderMus::HasCustomFormat(
 void OSExchangeDataProviderMus::SetFileContents(
     const base::FilePath& filename,
     const std::string& file_contents) {
-
 }
 #endif