Fix the HTML5 drag and drop demos on Linux and CrOS

ui/views/controls/textfield/textfield.cc

Index: ui/views/controls/textfield/textfield.cc
diff --git a/ui/views/controls/textfield/textfield.cc b/ui/views/controls/textfield/textfield.cc
index a1759901e6b01629360e529a462a91244c9503d2..8ca83cb0e93501fcd2275f9da6b61e02465dce3e 100644
--- a/ui/views/controls/textfield/textfield.cc
+++ b/ui/views/controls/textfield/textfield.cc
@@ -990,7 +990,6 @@ void Textfield::WriteDragDataForView(View* sender,
                                      const gfx::Point& press_pt,
                                      OSExchangeData* data) {
   const base::string16& selected_text(GetSelectedText());
-  data->SetString(selected_text);
   Label label(selected_text, GetFontList());
   label.SetBackgroundColor(GetBackgroundColor());
   label.set_subpixel_rendering_enabled(false);
@@ -1012,6 +1011,11 @@ void Textfield::WriteDragDataForView(View* sender,
   drag_utils::SetDragImageOnDataObject(*canvas, kOffset, data);
   if (controller_)
     controller_->OnWriteDragData(data);
+
+  // Set the string to |selected_text| if a string was not set by
+  // |controller_|.
+  if (!data->HasString())
+    data->SetString(selected_text);
 }
 
 int Textfield::GetDragOperationsForView(View* sender, const gfx::Point& p) {