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 f01bc14099cb782a4ad5503cbe418058c0d0c5a4..69163cbacfd12a8ab84a8619e532ad48413326b5 100644
--- a/chrome/common/extensions/api/extension_api.json
+++ b/chrome/common/extensions/api/extension_api.json
@@ -1005,7 +1005,25 @@
   },
   {
     "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",
@@ -1103,7 +1121,20 @@
         ]
       }
     ],
-    "events": []
+    "events": [
+      {
+        "name": "onChanged",
+        "type": "function",
+        "description": "Fired when one or more settings change.",
+        "parameters": [
+          {
+            "name": "changes",
+            "type": "array",
+            "items": {"$ref": "SettingChange"}
+          }
+        ]
+      }
+    ]
   },
   {
     "namespace": "windows",