Change the OOP PDF plugin to use BrowserPlugin mime type handling.

chrome/browser/resources/pdf/background.js

 // Copyright 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.
 
 (function() {
   'use strict';
 
   /**
-   * Keep a stack of stream details for requests. These are pushed onto the
-   * stack as requests come in and popped off the stack as they are handled by a
-   * renderer.
-   * TODO(raymes): This is probably racy for multiple requests. We could
-   * associate an ID with the request but this code will probably change
-   * completely when MIME type handling is improved.
+   * A map of view ID (which identifies a particular PDF viewer instance) to
+   * stream object.
+   * @type {Object.<string, Object>}
    */
-  var streamsCache = [];
+  var streams = {};
 
-  window.popStreamDetails = function() {
-    if (streamsCache.length > 0)
-      return streamsCache.pop();
-  };
+  /**
+   * A map of view ID (which identifies a particular PDF viewer instance) to
+   * initialization function for that view.
+   * @type {Object.<string, Function>}
+   */
+  var pluginInitFunctions = {};
 
+  /**
+   * If we have received a stream object and an initialization function for a
+   * particular PDF viewer instance we know that the extension has loaded in
+   * and we can pass it the stream. We can then delete the corresponding map
+   * entries.
+   * @param {string} viewId The ID of the view to initialize with a stream.
+   */
+  function flush(viewId) {
+    if (viewId in streams && viewId in pluginInitFunctions) {
+      pluginInitFunctions[viewId](streams[viewId]);
+      delete streams[viewId];
+      delete pluginInitFunctions[viewId];
+    }
+  }
+
+  /**
+   * This is called when loading a document with the PDF mime type and passes a
+   * stream that points to the PDF file. This may be run before or after we
+   * receive a message from the PDF viewer with its initialization function.
+   */
   chrome.streamsPrivate.onExecuteMimeTypeHandler.addListener(
     function(streamDetails) {
-      // TODO(raymes): Currently this doesn't work with embedded PDFs (it
-      // causes the entire frame to navigate). Also work out how we can
-      // mask the URL with the URL of the PDF.
-      streamsCache.push(streamDetails);
-      chrome.tabs.update(streamDetails.tabId, {url: 'index.html'});
+      // Store the stream until we are contacted by the PDF viewer that owns the
+      // stream.
+      streams[streamDetails.viewId] = streamDetails;
+      flush(streamDetails.viewId);
     }
   );
 
+  /**
+   * This is called when we receive a message from the PDF viewer indicating
+   * it has loaded and is ready to receive a stream of the data.
+   */
+  chrome.runtime.onMessage.addListener(
+    function(request, sender, responseFunction) {
+      // Store the initialization function until we receive the stream which
+      // corresponds to the PDF viewer.
+      pluginInitFunctions[request.viewId] = responseFunction;
+      flush(request.viewId);
+    }
+  );
 }());