Limit PDF helper extension to print preview only

chrome/browser/resources/pdf/browser_api.js

 // Copyright 2015 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.
 
 'use strict';
 
 /**
  * Returns a promise that will resolve to the default zoom factor.
  * @param {!Object} streamInfo The stream object pointing to the data contained
  *     in the PDF.
@@ skipping 130 matching lines @@
       listener(zoomChangeInfo.newZoomFactor);
     }.bind(this));
   }
 };
 
 /**
  * Creates a BrowserApi for an extension running as a mime handler.
  * @return {Promise<BrowserApi>} A promise to a BrowserApi instance constructed
  *     using the mimeHandlerPrivate API.
  */
 function createBrowserApiForMimeHandlerView() {

[raymes, 2016/10/13 00:43:22]

With my suggestion below, we won't throw an exception there - anymore. Instead
we will get 
"Unchecked runtime.lastError while running mimeHandlerPrivate.getStreamInfo:
Streams are only available from a mime handler view guest."

I think that exception is meaningful enough, so we can just test for the
presence of that.

[robwu, 2016/10/13 23:29:30]

Done.

   return new Promise(function(resolve, reject) {
     chrome.mimeHandlerPrivate.getStreamInfo(resolve);
   }).then(function(streamInfo) {
     let promises = [];
     let manageZoom = !streamInfo.embedded && streamInfo.tabId != -1;
     if (streamInfo.tabId != -1) {
       promises.push(new Promise(function(resolve) {
         chrome.tabs.get(streamInfo.tabId, resolve);
       }).then(function(tab) {
         if (tab)
@@ skipping 37 matching lines @@
     });
   }).then(function() { return BrowserApi.create(streamInfo, false); });
 }
 
 /**
  * Returns a promise that will resolve to a BrowserApi instance.
  * @return {Promise<BrowserApi>} A promise to a BrowserApi instance for the
  *     current environment.
  */
 function createBrowserApi() {
-  if (window.location.search)
+  if (location.search) {
+    if (location.ancestorOrigins[0] !== 'chrome://print') {

[raymes, 2016/10/12 02:08:52]

I think it could be good to rework these 2 checks. We should actually only ever
use the createBrowserApiForStandaloneExtension API when we're in print preview
(we could rename it to createBrowserApiForPrintPreview). We actually load the
pdf viewer in the context of chrome://print. So I think this can just boil down
to: 
if (document.location.origin == "chrome://print") 
  createBrowserApiForPrintPreview()

Similarly, in pdf.js, we should change this.isPrintPreview_ to check the same
thing. Could you add that to this CL?


In the plugin, we should do something similar (though this can go in a different
CL):
1) Change the IsPrintPreview() check to use the document URL
2) When we load a new pdf, to check that the URL being loaded is a
chrome://print URL.

[robwu, 2016/10/12 11:33:28]

Are you sure about the claim that this snippet runs in the context of
chrome://print? The source seems to show that chrome://print embeds the helper
extension in an iframe: 
https://chromium.googlesource.com/chromium/src/+blame/a223560fd493a9f25d23a33...
https://chromium.googlesource.com/chromium/src/+blame/a41883ee67ef28c0bd69aea...

[raymes, 2016/10/13 00:43:22]

Yes I'm fairly sure. PDFCreateOutOfProcessPlugin loads pdf_preview.html which is
loaded from chrome://print. You will be able to test it easily though, if my
assumption is false then print preview should be broken with the check I
suggested.

[robwu, 2016/10/13 23:29:30]

Done.

+      throw new Error('Refused to load the standalone extension.');
+    }
     return createBrowserApiForStandaloneExtension();
+  }
 
   return createBrowserApiForMimeHandlerView();
 }