Set a max limit on extension items' labels in context menus....

chrome/common/extensions/api/extension_api.json

 [
   {
     "namespace": "extension",
     "unprivileged": true,
     "types": [
       {
         "id": "MessageSender",
         "type": "object",
         "description": "An object containing information about the script context that sent a message or request.",
         "properties": {
@@ skipping 3013 matching lines @@
           {"type": "string", "name": "message"}
         ]
       },
       {
         "name": "createIncognitoTab",
         "type": "function",
         "description": "Creates an incognito tab during internal testing. Succeeds even if the extension is not enabled in incognito mode.",
         "parameters": [
           {"type": "string", "name": "url"}
         ]
+      },
+      {
+        "name": "sendMessage",
+        "type": "function",
+        "description": "Sends a string message to the browser process, generating a Notification that C++ test code can wait for.",
+        "parameters": [
+          {"type": "string", "name": "message"}
+        ]
       }
     ],
     "events": [
       {
         "name": "onMessage",
         "type": "function",
         "unprivileged": true,
         "description": "Used to test sending messages to extensions.",
         "parameters": [
           {
@@ skipping 167 matching lines @@
       {
         "name": "onInputCancelled",
         "perExtensionEvent": true,
         "type": "function",
         "description": "User has ended the keyword input session without accepting the input.",
         "parameters": []
       }
     ]
   }
 ]