Add wallpaper experimental api framework and add a simple category list.

chrome/common/extensions/api/experimental_wallpaper_manager.json

Index: chrome/common/extensions/api/experimental_wallpaper_manager.json
diff --git a/chrome/common/extensions/api/experimental_wallpaper_manager.json b/chrome/common/extensions/api/experimental_wallpaper_manager.json
new file mode 100644
index 0000000000000000000000000000000000000000..1528776dd701f0a87e2f7db3c16401c65ecb3e25
--- /dev/null
+++ b/chrome/common/extensions/api/experimental_wallpaper_manager.json
@@ -0,0 +1,31 @@
+// Copyright (c) 2012 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+[
+  {
+    "namespace":"experimental.wallpaperManager",
+    "nodoc": "true",
+    "functions": [
+      {
+        "name": "getStrings",
+        "type": "function",
+        "description": "Gets Strings.",
+        "nodoc": "true",
+        "parameters": [
+          {
+            "type": "function",
+            "name": "callback",
+            "parameters": [
+              {
+                "name": "result",
+                "type": "object",
+                "additionalProperties": {"type": "string"}
+              }
+            ]
+          }
+        ]
+      }
+    ]
+  }
+]