MD Extensions: Show messages for no extensions, and for no search results

chrome/browser/resources/md_extensions/item_list.js

Index: chrome/browser/resources/md_extensions/item_list.js
diff --git a/chrome/browser/resources/md_extensions/item_list.js b/chrome/browser/resources/md_extensions/item_list.js
index 109feeb337010a5799fe1b28548e582c9e6fbe60..a545b82e4c3786501e2bf6e3e96d06537aaa791b 100644
--- a/chrome/browser/resources/md_extensions/item_list.js
+++ b/chrome/browser/resources/md_extensions/item_list.js
@@ -21,6 +21,12 @@ cr.define('extensions', function() {
       },
 
       filter: String,
+
+      /** @private {Array<!chrome.developerPrivate.ExtensionInfo>} */
+      shownItems_: {
+        type: Array,
+        computed: 'computeShownItems_(items.*, filter)',
+      }
     },
 
     listeners: {
@@ -73,6 +79,15 @@ cr.define('extensions', function() {
         return item.name.toLowerCase().includes(this.filter.toLowerCase());
       }, this);
     },
+
+    shouldShowEmptyItemsMessage_: function() {
+      return this.items.length === 0;
+    },
+
+    shouldShowEmptySearchMessage_: function() {
+      return !this.shouldShowEmptyItemsMessage_() &&
+          this.shownItems_.length === 0;
+    },
   });
 
   return {