First shot at implementing drag&drop for Aura

ui/aura_shell/shell.cc

Index: ui/aura_shell/shell.cc
diff --git a/ui/aura_shell/shell.cc b/ui/aura_shell/shell.cc
index dc40423beb690ee3840f3c19588454a8548f6f58..189926900465880f2d572767c14f1ae5c471e131 100644
--- a/ui/aura_shell/shell.cc
+++ b/ui/aura_shell/shell.cc
@@ -7,6 +7,8 @@
 #include "base/bind.h"
 #include "base/command_line.h"
 #include "ui/aura/aura_switches.h"
+#include "ui/aura/client/aura_constants.h"
+#include "ui/aura/client/drag_drop_client.h"
 #include "ui/aura/desktop.h"
 #include "ui/aura/window.h"
 #include "ui/aura/window_types.h"
@@ -14,6 +16,7 @@
 #include "ui/aura_shell/default_container_layout_manager.h"
 #include "ui/aura_shell/desktop_event_filter.h"
 #include "ui/aura_shell/desktop_layout_manager.h"
+#include "ui/aura_shell/drag_drop_controller.h"
 #include "ui/aura_shell/launcher/launcher.h"
 #include "ui/aura_shell/shelf_layout_controller.h"
 #include "ui/aura_shell/shell_delegate.h"
@@ -89,6 +92,9 @@ Shell::Shell(ShellDelegate* delegate)
       new internal::DesktopEventFilter);
   aura::Desktop::GetInstance()->SetStackingClient(
       new internal::StackingController);
+  drag_drop_controller_.reset(new internal::DragDropController);
+  aura::Desktop::GetInstance()->SetProperty(aura::kDesktopDragDropClientKey,
+      static_cast<aura::DragDropClient*>(drag_drop_controller_.get()));
 }
 
 Shell::~Shell() {