Change OnWindowInputEvent to use display_id to find the host and update event root_location in WS.

services/ui/ws/window_manager_state.cc

Index: services/ui/ws/window_manager_state.cc
diff --git a/services/ui/ws/window_manager_state.cc b/services/ui/ws/window_manager_state.cc
index d9b9ed52c760fc9feb2932ce2b94462aeabe3a55..10de4a173f6eb76a02af581b99c2d45856ab563e 100644
--- a/services/ui/ws/window_manager_state.cc
+++ b/services/ui/ws/window_manager_state.cc
@@ -18,6 +18,7 @@
 #include "services/ui/ws/server_window.h"
 #include "services/ui/ws/user_display_manager.h"
 #include "services/ui/ws/user_id_tracker.h"
+#include "services/ui/ws/window_coordinate_conversions.h"
 #include "services/ui/ws/window_manager_display_root.h"
 #include "services/ui/ws/window_server.h"
 #include "services/ui/ws/window_tree.h"
@@ -581,12 +582,31 @@ void WindowManagerState::DispatchInputEventToWindow(ServerWindow* target,
                                                     const ui::Event& event,
                                                     Accelerator* accelerator) {
   DCHECK(IsActive());
+
+  std::unique_ptr<ui::Event> clone = ui::Event::Clone(event);
+  // Convert the root_location of this |event| to be from the coordinate system
+  // of the root window of the |window_tree_| to the coordinate system of the
+  // root_window of the window tree associated with this |client_id|.
+  if (client_id != window_tree_->id() && event.IsLocatedEvent()) {
+    WindowTree* target_tree = window_server()->GetTreeWithId(client_id);
+    DCHECK_GE(window_tree_->roots().size(), 1u);
+    DCHECK_GE(target_tree->roots().size(), 1u);
+    const ServerWindow* wm_root = window_tree_->FindRootFor(target);
+    const ServerWindow* target_root = target_tree->FindRootFor(target);
+    DCHECK(wm_root);
+    DCHECK(target_root);
+    DCHECK(wm_root->Contains(target_root));
+    gfx::Point new_root_location = ConvertPointBetweenWindows(
+        wm_root, target_root, event.AsLocatedEvent()->root_location());
+    clone->AsLocatedEvent()->set_root_location(new_root_location);
+  }
+
   // TODO(sky): this needs to see if another wms has capture and if so forward
   // to it.
   if (in_flight_event_details_) {
     std::unique_ptr<ProcessedEventTarget> processed_event_target(
         new ProcessedEventTarget(target, client_id, accelerator));
-    QueueEvent(event, std::move(processed_event_target),
+    QueueEvent(*clone, std::move(processed_event_target),
                event_processing_display_id_);
     return;
   }
@@ -594,7 +614,7 @@ void WindowManagerState::DispatchInputEventToWindow(ServerWindow* target,
   base::WeakPtr<Accelerator> weak_accelerator;
   if (accelerator)
     weak_accelerator = accelerator->GetWeakPtr();
-  DispatchInputEventToWindowImpl(target, client_id, event, weak_accelerator);
+  DispatchInputEventToWindowImpl(target, client_id, *clone, weak_accelerator);
 }
 
 ClientSpecificId WindowManagerState::GetEventTargetClientId(