Change streamsPrivate to use an IDL definition file.

chrome/common/extensions/api/streams_private.json

-// Copyright (c) 2013 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":"streamsPrivate",
-    "description": "none",
-    "events": [
-      {
-        "name": "onExecuteMimeTypeHandler",
-        "type": "function",
-        "description": "Fired when a resource is fetched which matches a mime type handled by this extension. The resource request is cancelled, and the extension is expected to handle the request. The event is restricted to a small number of white-listed extensions.",
-        "parameters": [
-          {
-            "name": "mimeType",
-            "type": "string",
-            "description": "The MIME type of the intercepted URL request."
-          },
-          {
-            "name": "originalUrl",
-            "type": "string",
-            "description": "The original URL that was intercepted."
-          },
-          {
-            "name": "streamUrl",
-            "type": "string",
-            "description": "The URL that the stream can be read from."
-          },
-          {
-            "name": "tabId",
-            "type": "integer",
-            "description": "The ID of the tab that opened the stream. If the stream is not opened in a tab, it will be -1."
-          },
-          {
-            "name": "expectedContentSize",
-            "type": "integer",
-            "description": "The amount of data the Stream should contain, if known.  If there is no information on the size it will be -1."
-          }
-        ]
-      }
-    ],
-
-    "functions": [
-    ]
-  }
-]
-