Fix an issue that referrer field is no longer exposed to pdfviewer

chrome/android/java/src/org/chromium/chrome/browser/externalnav/ExternalNavigationDelegateImpl.java

 // 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.
 
 package org.chromium.chrome.browser.externalnav;
 
 import android.Manifest.permission;
 import android.app.Activity;
 import android.content.Context;
 import android.content.DialogInterface;
@@ skipping 109 matching lines @@
                         activityResolved = true;
                         boolean canSelfOpen = false;
                         boolean hasPdfViewer = false;
                         for (ResolveInfo resolveInfo : handlers) {
                             String pName = resolveInfo.activityInfo.packageName;
                             if (packageName.equals(pName)) {
                                 canSelfOpen = true;
                             } else if (PDF_VIEWER.equals(pName)) {
                                 if (isPdfIntent(intent)) {
                                     intent.setClassName(pName, resolveInfo.activityInfo.name);
+                                    Uri referrer = new Uri.Builder().scheme(
+                                            IntentHandler.ANDROID_APP_REFERRER_SCHEME).authority(
+                                                    packageName).build();
+                                    intent.putExtra(Intent.EXTRA_REFERRER, referrer);
                                     hasPdfViewer = true;
                                     break;
                                 }
                             }
                         }
                         if ((canSelfOpen && !allowSelfOpen) && !hasPdfViewer) {
                             activityResolved = false;
                         }
                     }
                 }
@@ skipping 320 matching lines @@
         }
     }
 
     private void closeTab(Tab tab) {
         Context context = tab.getWindowAndroid().getContext().get();
         if (context instanceof ChromeActivity) {
             ((ChromeActivity) context).getTabModelSelector().closeTab(tab);
         }
     }
 }