[ash] Add TYPE_DIALOG and its item's LauncherContextMenu

ash/shelf/shelf_window_watcher_item_delegate.cc

Index: ash/shelf/shelf_window_watcher_item_delegate.cc
diff --git a/ash/shelf/shelf_window_watcher_item_delegate.cc b/ash/shelf/shelf_window_watcher_item_delegate.cc
index 6c7cc6565dcfda44f1298be9f9b0614ddaaed7b0..53fd1008088bf08cb06b264ec678198130dec13e 100644
--- a/ash/shelf/shelf_window_watcher_item_delegate.cc
+++ b/ash/shelf/shelf_window_watcher_item_delegate.cc
@@ -4,7 +4,10 @@
 
 #include "ash/shelf/shelf_window_watcher_item_delegate.h"
 
+#include "ash/shelf/shelf_model.h"
 #include "ash/shelf/shelf_util.h"
+#include "ash/shell.h"
+#include "ash/shell_delegate.h"
 #include "ash/wm/window_state.h"
 #include "ui/aura/window.h"
 #include "ui/views/corewm/window_animations.h"
@@ -14,8 +17,9 @@ namespace ash {
 namespace internal {
 
 ShelfWindowWatcherItemDelegate::ShelfWindowWatcherItemDelegate(
-    aura::Window* window)
-    : window_(window) {
+    aura::Window* window, ShelfModel* model)
+    : window_(window),
+      model_(model) {
 }
 
 ShelfWindowWatcherItemDelegate::~ShelfWindowWatcherItemDelegate() {
@@ -47,8 +51,11 @@ base::string16 ShelfWindowWatcherItemDelegate::GetTitle() {
 
 ui::MenuModel* ShelfWindowWatcherItemDelegate::CreateContextMenu(
     aura::Window* root_window) {
-  // TODO(simonhong): Create ShelfItemContextMenu.
-  return NULL;
+  ash::LauncherItem item =
+      *(model_->ItemByID(GetLauncherIDForWindow(window_)));
+  return Shell::GetInstance()->delegate()->CreateContextMenu(root_window,
+                                                             this,
+                                                             &item);
 }
 
 ShelfMenuModel* ShelfWindowWatcherItemDelegate::CreateApplicationMenu(