aura-mus: add a drag representation image.

services/ui/public/interfaces/window_tree_constants.mojom

Index: services/ui/public/interfaces/window_tree_constants.mojom
diff --git a/services/ui/public/interfaces/window_tree_constants.mojom b/services/ui/public/interfaces/window_tree_constants.mojom
index 19a5fdf11af87d167694eca94c9d0d2ca02cb768..bf2552a31ff98e7f9c5d8578ada6ad35848d4d1b 100644
--- a/services/ui/public/interfaces/window_tree_constants.mojom
+++ b/services/ui/public/interfaces/window_tree_constants.mojom
@@ -56,6 +56,12 @@ const uint32 kDropEffectMove = 1;
 const uint32 kDropEffectCopy = 2;
 const uint32 kDropEffectLink = 4;
 
+// Whether a drag was caused by mouse or touch.
+enum DragEventSource {

[sky, 2017/03/23 00:05:36]

Would it make sense to replace this with PointerKind? The enum includes PEN, but
that should be a valid drag source too.

[Elliot Glaysher, 2017/03/23 19:58:44]

Removed this and moved to PointerKind. I'm collapsing pen and touch into the
same ui::DragTypes::DragEventSource on both sides, but that appears to be the
current behaviour.

+  MOUSE = 0,
+  TOUCH
+};
+
 // When this flag is set in a call to Embed(), the embedder (i.e. the client
 // that is making the call to Embed()) will receive events that are targeted to
 // the embedded client. The embedded client will not receive any input events