mus: Use the new drag API to implement tab dragging in chrome.

chrome/browser/ui/views/tabs/window_finder_mus.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "chrome/browser/ui/views/tabs/window_finder_mus.h"
+
+#include "ui/aura/window.h"
+#include "ui/views/mus/native_widget_mus.h"
+#include "ui/views/mus/window_manager_connection.h"
+
+WindowFinderMus::WindowFinderMus() {}
+
+WindowFinderMus::~WindowFinderMus() {}
+
+gfx::NativeWindow WindowFinderMus::GetLocalProcessWindowAtPoint(
+    const gfx::Point& screen_point,
+    const std::set<gfx::NativeWindow>& ignore) {
+  std::set<ui::Window*> mus_windows =
+      views::WindowManagerConnection::Get()->GetRoots();
+  // TODO(erg): Needs to deal with stacking order here.
+
+  // For every mus window, look at the associated aura window and see if we're
+  // in that.
+  for (ui::Window* mus : mus_windows) {
+    views::Widget* widget = views::NativeWidgetMus::GetWidgetForWindow(mus);
+    if (widget && widget->GetWindowBoundsInScreen().Contains(screen_point)) {
+      aura::Window* content_window = widget->GetNativeWindow();
+
+      // If we were instructed to ignore this window, ignore it.
+      if (ContainsKey(ignore, content_window))
+        continue;
+
+      return content_window;
+    }
+  }
+
+  return nullptr;
+}