First shot at implementing drag&drop for Aura

ui/aura_shell/drag_image_view.cc

+// Copyright (c) 2011 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 "ui/aura_shell/drag_image_view.h"
+
+#include "views/widget/widget.h"
+
+namespace aura_shell {
+namespace internal {
+
+namespace {
+using views::Widget;
+
+Widget* CreateDragWidget() {
+  Widget* drag_widget = new Widget;
+  Widget::InitParams params;
+  params.type = Widget::InitParams::TYPE_TOOLTIP;
+  params.keep_on_top = true;
+  params.accept_events = false;
+  params.ownership = Widget::InitParams::WIDGET_OWNS_NATIVE_WIDGET;
+  params.transparent = true;
+  drag_widget->Init(params);
+  drag_widget->SetOpacity(0xFF);
+  return drag_widget;
+}
+}
+
+DragImageView::DragImageView() : views::ImageView() {
+  widget_.reset(CreateDragWidget());
+  widget_->SetContentsView(this);
+  widget_->SetAlwaysOnTop(true);
+
+  // We are owned by the DragDropController.
+  set_parent_owned(false);
+}
+
+DragImageView::~DragImageView() {
+  widget_->Hide();
+}
+
+void DragImageView::SetScreenBounds(const gfx::Rect& bounds) {
+  widget_->SetBounds(bounds);
+}
+
+void DragImageView::SetScreenPosition(const gfx::Point& position) {
+  widget_->SetBounds(gfx::Rect(position, GetPreferredSize()));
+}
+
+void DragImageView::SetVisible(bool visible) {

[Ben Goodger (Google), 2011/11/16 00:13:20]

This feels weird. In general I dislike overriding. Can we move this onto a
separate Show() method so we don't muck with the view's visibility state?

[varunjain, 2011/11/16 20:30:15]

Done.

+  // We simply show/hide the container widget.
+  if (visible != widget_->IsVisible()) {
+    if (visible)
+      widget_->Show();
+    else
+      widget_->Hide();
+  }
+  View::SetVisible(visible);
+}
+
+}  // namespace internal
+}  // namespace aura_shell