mash: Move ShelfWindowWatcher[ItemDelegate] to ash/common.

ash/mus/bridge/wm_window_mus.cc

Index: ash/mus/bridge/wm_window_mus.cc
diff --git a/ash/mus/bridge/wm_window_mus.cc b/ash/mus/bridge/wm_window_mus.cc
index 0418d4068f557cbe8801f3ac57dfa786223f7687..84525e07fd48ae8cd90771b9255f4fa23c16f0c5 100644
--- a/ash/mus/bridge/wm_window_mus.cc
+++ b/ash/mus/bridge/wm_window_mus.cc
@@ -355,10 +355,18 @@ void WmWindowMus::SetIntProperty(WmWindowProperty key, int value) {
 }
 
 ShelfItemDetails* WmWindowMus::GetShelfItemDetails() {
-  NOTIMPLEMENTED();
+  NOTIMPLEMENTED();  // TODO: Add support; see crbug.com/634150
   return nullptr;
 }
 
+void WmWindowMus::SetShelfItemDetails(const ShelfItemDetails& details) {
+  NOTIMPLEMENTED();  // TODO: Add support; see crbug.com/634150
+}
+
+void WmWindowMus::ClearShelfItemDetails() {
+  NOTIMPLEMENTED();  // TODO: Add support; see crbug.com/634150
+}
+
 const wm::WindowState* WmWindowMus::GetWindowState() const {
   return window_state_.get();
 }