Add onChanged events to the extension settings API, both from sync and between

chrome/common/extensions/api/extension_api.json

Index: chrome/common/extensions/api/extension_api.json
diff --git a/chrome/common/extensions/api/extension_api.json b/chrome/common/extensions/api/extension_api.json
index 73889367a46524184d6ec70184ff25f871ca88e8..fae27ea77c8dcc4833445725fc57fc52b53213c9 100644
--- a/chrome/common/extensions/api/extension_api.json
+++ b/chrome/common/extensions/api/extension_api.json
@@ -1019,7 +1019,25 @@
   },
   {
     "namespace": "experimental.settings",
-    "types": [],
+    "types": [
+      {
+        "id": "SettingChange",
+        "type": "object",
+        "properties": {
+          "key": {"type": "string", "description": "The ID of the setting which changed."},
+          "oldValue": {
+            "type": "any",
+            "description": "The old value of the setting, before it changed.",
+            "optional": true
+          },
+          "newValue": {
+            "type": "any",
+            "description": "The new value of the setting.",
+            "optional": true
+          }
+        }
+      }
+    ],
     "functions": [
       {
         "name": "get",
@@ -1117,7 +1135,20 @@
         ]
       }
     ],
-    "events": []
+    "events": [
+      {
+        "name": "onChanged",
+        "type": "function",
+        "description": "Fired when one or more settings change.",
+        "parameters": [
+          {
+            "name": "changes",
+            "type": "array",
+            "items": {"$ref": "SettingChange"}
+          }
+        ]
+      }
+    ]
   },
   {
     "namespace": "windows",