chromeos: Rename ash::WmShelf to Shelf

ash/BUILD.gn

Index: ash/BUILD.gn
diff --git a/ash/BUILD.gn b/ash/BUILD.gn
index d8f4f27d37cd1cec01604a900a221bfb4137cba7..6be4d02c8a4ea1953ab67cd8c1629111e8a60608 100644
--- a/ash/BUILD.gn
+++ b/ash/BUILD.gn
@@ -284,6 +284,8 @@ component("ash") {
     "shelf/overflow_bubble_view.h",
     "shelf/overflow_button.cc",
     "shelf/overflow_button.h",
+    "shelf/shelf.cc",
+    "shelf/shelf.h",
     "shelf/shelf_alignment_menu.cc",
     "shelf/shelf_alignment_menu.h",
     "shelf/shelf_application_menu_model.cc",
@@ -308,6 +310,7 @@ component("ash") {
     "shelf/shelf_model.cc",
     "shelf/shelf_model.h",
     "shelf/shelf_model_observer.h",
+    "shelf/shelf_observer.h",
     "shelf/shelf_tooltip_manager.cc",
     "shelf/shelf_tooltip_manager.h",
     "shelf/shelf_view.cc",
@@ -320,9 +323,6 @@ component("ash") {
     "shelf/shelf_window_watcher.h",
     "shelf/shelf_window_watcher_item_delegate.cc",
     "shelf/shelf_window_watcher_item_delegate.h",
-    "shelf/wm_shelf.cc",
-    "shelf/wm_shelf.h",
-    "shelf/wm_shelf_observer.h",
     "shell.cc",
     "shell.h",
     "shell_delegate.h",