Propagate drag-and-drop key modifiers to WebView's guest renderer.

content/renderer/drop_data_builder.cc

Index: content/renderer/drop_data_builder.cc
diff --git a/content/renderer/drop_data_builder.cc b/content/renderer/drop_data_builder.cc
index 37b723130fc1b00bdb2eb0c47c09458de54e84fe..5af68e0639830be669a97a0502d95ad7466f9d7e 100644
--- a/content/renderer/drop_data_builder.cc
+++ b/content/renderer/drop_data_builder.cc
@@ -19,6 +19,7 @@ namespace content {
 // static
 DropData DropDataBuilder::Build(const WebDragData& drag_data) {
   DropData result;
+  result.key_modifiers = drag_data.modifierKeyState();
   result.referrer_policy = blink::WebReferrerPolicyDefault;
 
   const WebVector<WebDragData::Item>& item_list = drag_data.items();