Change streamsPrivate to use an IDL definition file.

chrome/common/extensions/api/streams_private.idl

+// Copyright 2014 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 {
+  interface Events {
+    // 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.
+    static void onExecuteMimeTypeHandler(
+      // The MIME type of the intercepted URL request.
+      DOMString mimeType,
+      // The original URL that was intercepted.
+      DOMString originalUrl,
+      // The URL that the stream can be read from.
+      DOMString streamUrl,
+      // The ID of the tab that opened the stream. If the stream is not opened
+      // in a tab, it will be -1.
+      long tabId,
+      // The amount of data the Stream should contain, if known.  If there is
+      // no information on the size it will be -1.
+      long expectedContentSize);
+  };
+};