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 d8e729937627fdc0f9721979e550e9de4ceb8a95..f06a4be26734be20481c1c6a2d9df15fed8ae6ee 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": {

[Matt Perry, 2011/10/07 22:39:52]

can you think of a use case for needing the old value? i would expect extensions
to only care:
(a) that a particular key has changed, and/or
(b) what the new value of the key is.

[not at google - send to devlin, 2011/10/10 01:00:16]

I would expect that too.  However... I made it this way because the HTML event
for localStorage changes has key/newValue/oldValue and I figured it can't hurt
to just match it.

I could imagine it helping with debugging for extension authors perhaps?

[Matt Perry, 2011/10/10 20:37:15]

OK, fair enough.

+            "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",