Limit PDF helper extension to print preview only

chrome/browser/resources/pdf/browser_api.js

Index: chrome/browser/resources/pdf/browser_api.js
diff --git a/chrome/browser/resources/pdf/browser_api.js b/chrome/browser/resources/pdf/browser_api.js
index 90033b84085322370cabe103d2970fd738817a56..051a5aff5bcf490d7bb44f3e0111705a001c140e 100644
--- a/chrome/browser/resources/pdf/browser_api.js
+++ b/chrome/browser/resources/pdf/browser_api.js
@@ -206,8 +206,12 @@ function createBrowserApiForStandaloneExtension() {
  *     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();
 }