MD-Extension: Make extension vs app detection logic more robust.

R=scottchen@chromium.org

Bug: NONE
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ic85659a4598037f029f49f3ce073f4b53ac3860f
Reviewed-on: https://chromium-review.googlesource.com/790941Reviewed-by: Scott Chen <scottchen@chromium.org>
Commit-Queue: Hector Carmona <hcarmona@chromium.org>
Cr-Commit-Position: refs/heads/master@{#519768}

chrome/browser/resources/md_extensions/item_behavior.js

@@ -12,9 +12,17 @@ cr.define('extensions', function() {
      * @return {string} The app or extension label depending on |type|.
      */
     appOrExtension: function(type, appLabel, extensionLabel) {
-      return (type == chrome.developerPrivate.ExtensionType.EXTENSION) ?
-          extensionLabel :
-          appLabel;
+      const ExtensionType = chrome.developerPrivate.ExtensionType;
+      switch (type) {
+        case ExtensionType.HOSTED_APP:
+        case ExtensionType.LEGACY_PACKAGED_APP:
+        case ExtensionType.PLATFORM_APP:
+          return appLabel;
+        case ExtensionType.EXTENSION:
+        case ExtensionType.SHARED_MODULE:
+          return extensionLabel;
+      }
+      assertNotReached('Item type is not App or Extension.');
     },
   };