Refactors MultiWindowResizeController to use ash/wm/common

ash/wm/aura/wm_root_window_controller_aura.cc

Index: ash/wm/aura/wm_root_window_controller_aura.cc
diff --git a/ash/wm/aura/wm_root_window_controller_aura.cc b/ash/wm/aura/wm_root_window_controller_aura.cc
index ed6f18ccc1f8089df734e6a81030adb0f42fa9c2..976a3359954c13bae5f99d33ec5f047508129bf0 100644
--- a/ash/wm/aura/wm_root_window_controller_aura.cc
+++ b/ash/wm/aura/wm_root_window_controller_aura.cc
@@ -16,6 +16,8 @@
 #include "ash/wm/workspace_controller.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_property.h"
+#include "ui/events/event_targeter.h"
+#include "ui/events/event_utils.h"
 
 DECLARE_WINDOW_PROPERTY_TYPE(ash::wm::WmRootWindowControllerAura*);
 
@@ -101,6 +103,20 @@ void WmRootWindowControllerAura::ConfigureWidgetInitParamsForContainer(
       root_window_controller_->GetRootWindow(), shell_container_id);
 }
 
+WmWindow* WmRootWindowControllerAura::FindEventTarget(
+    const gfx::Point& location_in_screen) {
+  gfx::Point location_in_root =
+      GetWindow()->ConvertPointFromScreen(location_in_screen);
+  aura::Window* root = root_window_controller_->GetRootWindow();
+  ui::MouseEvent test_event(ui::ET_MOUSE_MOVED, location_in_root,
+                            location_in_root, ui::EventTimeForNow(),
+                            ui::EF_NONE, ui::EF_NONE);
+  ui::EventTarget* event_handler = static_cast<ui::EventTarget*>(root)
+                                       ->GetEventTargeter()
+                                       ->FindTargetForEvent(root, &test_event);
+  return WmWindowAura::Get(static_cast<aura::Window*>(event_handler));
+}
+
 void WmRootWindowControllerAura::AddObserver(
     WmRootWindowControllerObserver* observer) {
   observers_.AddObserver(observer);