Extension half of the proxy error event

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 3790 matching lines @@
             "parameters": [
               {
                 "name": "config",
                 "$ref": "ProxyConfig",
                 "description": "Configuration, not necessarily a literal copy of the configuration passed to useCustomProxySettings()."
               }
             ]
           }
         ]
       }
+    ],
+    "events": [
+      {
+        "name": "onProxyError",
+        "type": "function",
+        "description": "Notifies about proxy errors.",
+        "parameters": [
+          {
+            "type": "object",
+            "name": "details",
+            "properties": {
+              "fatal": {
+                "type": "boolean",
+                "description": "If true, the error was fatal and the network transaction was aborted. Otherwise, a direct connection is used instead."
+              },
+              "error": {
+                "type": "string",
+                "description": "The error description."
+              },
+              "details": {
+                "type": "string",
+                "description": "Additional details about the error such as a JavaScript runtime error."
+              }
+            }
+          }
+        ]
+      }
     ]
   },
   {
     "namespace": "experimental.clipboard",
     "types": [],
     "functions": [
       {
         "name": "executeCopy",
         "type": "function",
         "description": "Triggers a copy operation in the specified tab.",
@@ skipping 705 matching lines @@
                   "token": { "type": "string", "optional": true }
                 }
               }
             ]
           }
         ]
       }
     ]
   }
 ]