Clean up how we handle themes in the extensions system and management API....

chrome/common/extensions/api/extension_api.json

Index: chrome/common/extensions/api/extension_api.json
===================================================================
--- chrome/common/extensions/api/extension_api.json	(revision 75613)
+++ chrome/common/extensions/api/extension_api.json	(working copy)
@@ -4265,6 +4265,10 @@
             "description": "True if this is an app.",
             "type": "boolean"
           },
+          "isTheme": {
+            "description": "True if this is a theme.",
+            "type": "boolean"
+          },
           "appLaunchUrl": {
             "description": "The launch url (only present for apps).",
             "type": "string",
@@ -4426,7 +4430,7 @@
       },
       {
         "name": "onDisabled",
-        "description": "Fired when an app or extension has been disabled",
+        "description": "Fired when an app or extension has been disabled.",
         "type": "function",
         "parameters": [{"name": "info", "$ref":"ExtensionInfo"}]
       }