mash: Add shelf context menu support.

Chrome serializes its shelf item context menus for Ash.
Ash displays the menus and reports invocations to Chrome.

Add an ash-side ShelfContextMenu class that supports:
-Local menu items to set shelf & wallpaper prefs/settings.
-Proxies Chrome's menu items via mojo structs/interfaces.
-Also used for wallpaper/desktop context menus (via RWC).

Add ash::mojom::ShelfItemDelegate::GetContextMenuItems, etc.:
-Extend ExecuteCommand, MenuItem, etc. to support context menus.
-Denote the command's origin (context/app menu) and display id.
-Allow 64-bit int command and radio-group ids; null images.
-Add ash::mojom::MenuItemType=ui::MenuModel::ItemType traits.

Add common ash::ShelfItemDelegate context menu handling:
-Subclasses override new virtual GetContextMenu() helper.
-GetContextMenuItems() stores the MenuModel for execution.
-ExecuteContextMenuCommand() handles context menu invocation.

Wire up chrome's launcher item subclass context menus.
Make minor launcher context menu class simplifications.
Add a ShelfWindowWatcher context menu item for closing.

Remove mus, ash_shell, test, and desktop context menu classes.
Remove ShellDelegate::CreateContextMenu and ash::ShelfAlignmentMenu.
Inline CanChangeShelfAlignment; move CanUserModifyShelfAutoHideBehavior.
Add unit tests, flip TestWallpaperDelegate::CanOpenSetWallpaperPage.

Bug: 640693, 753028
Test: No Chrome OS shelf/desktop context menu behavior changes.
Change-Id: I3afb93095b4042dca57d16844c5b05308f06a384
TBR: caitkp@chromium.org
Reviewed-on: https://chromium-review.googlesource.com/571517
Commit-Queue: Michael Wasserman <msw@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: James Cook <jamescook@chromium.org>
Cr-Commit-Position: refs/heads/master@{#495735}

• ash/BUILD.gn[diff]
• ash/DEPS[diff]
• ash/mus/BUILD.gn[diff]
• ash/mus/context_menu_mus.cc[Deleted - diff]
• ash/mus/context_menu_mus.h[Deleted - diff]
• ash/mus/shell_delegate_mus.cc[diff]
• ash/mus/shell_delegate_mus.h[diff]
• ash/public/cpp/remote_shelf_item_delegate.cc[diff]
• ash/public/cpp/remote_shelf_item_delegate.h[diff]
• ash/public/cpp/shelf_item_delegate.cc[diff]
• ash/public/cpp/shelf_item_delegate.h[diff]
• ash/public/cpp/shelf_prefs.cc[diff]
• ash/public/cpp/shelf_prefs.h[diff]
• ash/public/cpp/shelf_struct_traits.h[diff]
• ash/public/interfaces/shelf.mojom[diff]
• ash/public/interfaces/shelf.typemap[diff]
• ash/root_window_controller.cc[diff]
• ash/shelf/app_list_shelf_item_delegate.cc[diff]
• ash/shelf/app_list_shelf_item_delegate.h[diff]
• ash/shelf/shelf.cc[diff]
• ash/shelf/shelf.h[diff]
• ash/shelf/shelf_alignment_menu.h[Deleted - diff]
• ash/shelf/shelf_application_menu_model.cc[diff]
• ash/shelf/shelf_context_menu_model.cc[Added - diff]
• ash/shelf/shelf_context_menu_model.h[Added - diff]
• ash/shelf/shelf_context_menu_model_unittest.cc[Added - diff]
• ash/shelf/shelf_view.cc[diff]
• ash/shelf/shelf_view.h[diff]
• ash/shelf/shelf_view_test_api.cc[diff]
• ash/shelf/shelf_view_test_api.h[diff]
• ash/shelf/shelf_view_unittest.cc[diff]
• ash/shelf/shelf_window_watcher_item_delegate.cc[diff]
• ash/shelf/shelf_window_watcher_item_delegate.h[diff]
• ash/shell/context_menu.cc[Deleted - diff]
• ash/shell/context_menu.h[Deleted - diff]
• ash/shell/shell_delegate_impl.cc[diff]
• ash/shell/shell_delegate_impl.h[diff]
• ash/shell/window_watcher_shelf_item_delegate.cc[diff]
• ash/shell/window_watcher_shelf_item_delegate.h[diff]
• ash/shell_delegate.h[diff]
• ash/shell_port.cc[diff]
• ash/strings/BUILD.gn[diff]
• ash/test_shell_delegate.cc[diff]
• ash/test_shell_delegate.h[diff]
• ash/wallpaper/test_wallpaper_delegate.cc[diff]
• ash/wallpaper/test_wallpaper_delegate.h[diff]
• chrome/browser/ui/BUILD.gn[diff]
• chrome/browser/ui/ash/chrome_shell_delegate.cc[diff]
• chrome/browser/ui/ash/chrome_shell_delegate.h[diff]
• chrome/browser/ui/ash/launcher/app_shortcut_launcher_item_controller.cc[diff]
• chrome/browser/ui/ash/launcher/app_shortcut_launcher_item_controller.h[diff]
• chrome/browser/ui/ash/launcher/app_window_launcher_item_controller.cc[diff]
• chrome/browser/ui/ash/launcher/app_window_launcher_item_controller.h[diff]
• chrome/browser/ui/ash/launcher/arc_app_deferred_launcher_item_controller.cc[diff]
• chrome/browser/ui/ash/launcher/arc_app_deferred_launcher_item_controller.h[diff]
• chrome/browser/ui/ash/launcher/arc_app_window_launcher_item_controller.cc[diff]
• chrome/browser/ui/ash/launcher/arc_app_window_launcher_item_controller.h[diff]
• chrome/browser/ui/ash/launcher/arc_launcher_context_menu.cc[diff]
• chrome/browser/ui/ash/launcher/arc_launcher_context_menu.h[diff]
• chrome/browser/ui/ash/launcher/browser_shortcut_launcher_item_controller.cc[diff]
• chrome/browser/ui/ash/launcher/browser_shortcut_launcher_item_controller.h[diff]
• chrome/browser/ui/ash/launcher/chrome_launcher_controller_browsertest.cc[diff]
• chrome/browser/ui/ash/launcher/chrome_launcher_controller_unittest.cc[diff]
• chrome/browser/ui/ash/launcher/desktop_shell_launcher_context_menu.cc[Deleted - diff]
• chrome/browser/ui/ash/launcher/desktop_shell_launcher_context_menu.h[Deleted - diff]
• chrome/browser/ui/ash/launcher/extension_app_window_launcher_item_controller.cc[diff]
• chrome/browser/ui/ash/launcher/extension_app_window_launcher_item_controller.h[diff]
• chrome/browser/ui/ash/launcher/extension_launcher_context_menu.cc[diff]
• chrome/browser/ui/ash/launcher/extension_launcher_context_menu.h[diff]
• chrome/browser/ui/ash/launcher/launcher_context_menu.cc[diff]
• chrome/browser/ui/ash/launcher/launcher_context_menu.h[diff]
• chrome/browser/ui/ash/launcher/launcher_context_menu_unittest.cc[diff]