Fix mash shelf id mapping and removal.

Add ShelfID to app_id mapping, to complement the inverse map.
(these are 1-to-1 mappings, but two maps eases usage)

Remove mappings when shelf items are removed.
Implement the ShelfDelegate interface mapping functions.

TODO: Add unit/shell testing of ShelfDelegateMus.

BUG=607271
TEST=|ShelfDelegaeMus::app_id_to_shelf_id_| shrinks as appropriate.
R=sadrul@chromium.org,sky@chromium.org

Review-Url: https://codereview.chromium.org/1932503002
Cr-Commit-Position: refs/heads/master@{#390289}

ash/mus/shelf_delegate_mus.cc

@@ -216,17 +216,18 @@ void ShelfDelegateMus::OnShelfAutoHideBehaviorChanged(Shelf* shelf) {
 }
 
 ShelfID ShelfDelegateMus::GetShelfIDForAppID(const std::string& app_id) {
-  NOTIMPLEMENTED();
+  if (app_id_to_shelf_id_.count(app_id))
+    return app_id_to_shelf_id_[app_id];
   return 0;
 }
 
 bool ShelfDelegateMus::HasShelfIDToAppIDMapping(ShelfID id) const {
-  NOTIMPLEMENTED();
-  return false;
+  return shelf_id_to_app_id_.count(id) != 0;
 }
 
 const std::string& ShelfDelegateMus::GetAppIDForShelfID(ShelfID id) {
-  NOTIMPLEMENTED();
+  if (shelf_id_to_app_id_.count(id))
+    return shelf_id_to_app_id_[id];
   return base::EmptyString();
 }
 
@@ -282,6 +283,7 @@ void ShelfDelegateMus::PinItem(
 
   ShelfID shelf_id = model_->next_id();
   app_id_to_shelf_id_.insert(std::make_pair(app_id, shelf_id));
+  shelf_id_to_app_id_.insert(std::make_pair(shelf_id, app_id));
 
   ShelfItem shelf_item;
   shelf_item.type = TYPE_APP_SHORTCUT;
@@ -304,8 +306,11 @@ void ShelfDelegateMus::UnpinItem(const mojo::String& app_id) {
   ShelfItemDelegateMus* item_delegate = GetShelfItemDelegate(shelf_id);
   DCHECK(item_delegate->pinned());
   item_delegate->set_pinned(false);
-  if (item_delegate->window_id_to_title().empty())
+  if (item_delegate->window_id_to_title().empty()) {
     model_->RemoveItemAt(model_->ItemIndexByID(shelf_id));
+    app_id_to_shelf_id_.erase(app_id.To<std::string>());
+    shelf_id_to_app_id_.erase(shelf_id);
+  }
 }
 
 void ShelfDelegateMus::OnUserWindowObserverAdded(
@@ -334,6 +339,7 @@ void ShelfDelegateMus::OnUserWindowAdded(
   window_id_to_shelf_id_.insert(
       std::make_pair(user_window->window_id, shelf_id));
   app_id_to_shelf_id_.insert(std::make_pair(app_id, shelf_id));
+  shelf_id_to_app_id_.insert(std::make_pair(shelf_id, app_id));
 
   ShelfItem item;
   item.type = TYPE_PLATFORM_APP;
@@ -355,8 +361,12 @@ void ShelfDelegateMus::OnUserWindowRemoved(uint32_t window_id) {
   ShelfItemDelegateMus* item_delegate = GetShelfItemDelegate(shelf_id);
   item_delegate->RemoveWindow(window_id);
   window_id_to_shelf_id_.erase(window_id);
-  if (item_delegate->window_id_to_title().empty() && !item_delegate->pinned())
+  if (item_delegate->window_id_to_title().empty() && !item_delegate->pinned()) {
     model_->RemoveItemAt(model_->ItemIndexByID(shelf_id));
+    const std::string& app_id = shelf_id_to_app_id_[shelf_id];
+    app_id_to_shelf_id_.erase(app_id);
+    shelf_id_to_app_id_.erase(shelf_id);
+  }
 }
 
 void ShelfDelegateMus::OnUserWindowTitleChanged(

ash/mus/shelf_delegate_mus.h

@@ -75,6 +75,7 @@ class ShelfDelegateMus : public ShelfDelegate,
   std::map<uint32_t, ShelfID> window_id_to_shelf_id_;
 
   std::map<std::string, ShelfID> app_id_to_shelf_id_;
+  std::map<ShelfID, std::string> shelf_id_to_app_id_;
 
   DISALLOW_COPY_AND_ASSIGN(ShelfDelegateMus);
 };