PDF Viewer: Fix regression causing password prompt to not show up.

Fixed: 1102943
Change-Id: Ic44bf23de891295106fa73092c14f9a17672fd16
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2285383
Commit-Queue: dpapad <dpapad@chromium.org>
Commit-Queue: Rebekah Potter <rbpotter@chromium.org>
Auto-Submit: dpapad <dpapad@chromium.org>
Reviewed-by: Rebekah Potter <rbpotter@chromium.org>
Cr-Commit-Position: refs/heads/master@{#786100}

chrome/browser/resources/pdf/pdf_viewer.js

@@ -762,7 +762,7 @@ class PDFViewerElement extends PDFViewerBaseElement {
     // responding to an incorrect password so deny it.
     const passwordScreen = this.$$('#password-screen');
     assert(passwordScreen);
-    if (passwordScreen.active) {
+    if (!passwordScreen.active) {
       this.hadPassword_ = true;
       passwordScreen.show();
     } else {