Hide dismiss button on toast when doing partial screenshot using stylus tools.

ash/common/system/toast/toast_data.cc

Index: ash/common/system/toast/toast_data.cc
diff --git a/ash/common/system/toast/toast_data.cc b/ash/common/system/toast/toast_data.cc
index 2b7fa9072153571b2f890bc010197ee44dc25400..5390b781e25f195a1dec5973720598e411853ff8 100644
--- a/ash/common/system/toast/toast_data.cc
+++ b/ash/common/system/toast/toast_data.cc
@@ -11,7 +11,7 @@ namespace ash {
 ToastData::ToastData(std::string id,
                      const base::string16& text,
                      int32_t duration_ms,
-                     const base::string16& dismiss_text)
+                     const base::Optional<base::string16>& dismiss_text)
     : id(std::move(id)),
       text(text),
       duration_ms(duration_ms),
@@ -19,4 +19,6 @@ ToastData::ToastData(std::string id,
 
 ToastData::ToastData(const ToastData& other) = default;
 
+ToastData::~ToastData() = default;
+
 }  // namespace ash