Add new wallpaper app icons

BUG=371859

Review URL: https://codereview.chromium.org/935053003

Cr-Commit-Position: refs/heads/master@{#317330}

chrome/browser/resources/chromeos/wallpaper_manager/manifest.json

@@ -8,7 +8,13 @@
   "manifest_version": 2,
   "description": "An experimental wallpaper picker UI",
   "icons": {
-    "128": "images/icon128.png"
+    "16": "images/icon16.png",
+    "32": "images/icon32.png",
+    "48": "images/icon48.png",
+    "64": "images/icon64.png",
+    "96": "images/icon96.png",
+    "128": "images/icon128.png",
+    "256": "images/icon256.png"
   },
   "permissions": [
     "alarms",