Make shelf item can be dragged when context menu is opened.

ui/views/controls/menu/menu_runner_impl.cc

 // Copyright 2014 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/views/controls/menu/menu_runner_impl.h"
 
 #include "build/build_config.h"
 #include "ui/native_theme/native_theme.h"
 #include "ui/views/controls/button/menu_button.h"
 #include "ui/views/controls/menu/menu_controller.h"
@@ skipping 104 matching lines @@
   running_ = true;
   for_drop_ = (run_types & MenuRunner::FOR_DROP) != 0;
   bool has_mnemonics = (run_types & MenuRunner::HAS_MNEMONICS) != 0;
   owns_controller_ = false;
   if (!controller) {
     // No menus are showing, show one.
     controller = new MenuController(!for_drop_, this);
     owns_controller_ = true;
   }
   controller->set_is_combobox((run_types & MenuRunner::COMBOBOX) != 0);
+  if (run_types & MenuRunner::FIXED_ANCHOR) {

[xiyuan, 2017/05/12 20:24:57]

We probably should make ShelfView to call set_cancel_active_touches instead of
relying on |run_types|.

+    controller->set_cancel_active_touches(false);
+  }
   controller_ = controller->AsWeakPtr();
   menu_->set_controller(controller_.get());
   menu_->PrepareForRun(owns_controller_,
                        has_mnemonics,
                        !for_drop_ && ShouldShowMnemonics(button));
 
   controller->Run(parent, button, menu_, bounds, anchor,
                   (run_types & MenuRunner::CONTEXT_MENU) != 0,
                   (run_types & MenuRunner::NESTED_DRAG) != 0);
 }
@@ skipping 61 matching lines @@
 #if defined(OS_WIN)
   // This is only needed on Windows.
   if (!show_mnemonics)
     show_mnemonics = ui::win::IsAltPressed();
 #endif
   return show_mnemonics;
 }
 
 }  // namespace internal
 }  // namespace views