Disable external navigation for file downloads.

chrome/android/java/src/org/chromium/chrome/browser/externalnav/ExternalNavigationHandler.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.content.ActivityNotFoundException;
 import android.content.ComponentName;
 import android.content.Intent;
 import android.content.pm.ResolveInfo;
@@ skipping 131 matching lines @@
         // http://crbug.com/441284 : Disallow firing external intent while Chrome is in the
         // background.
         if (params.isApplicationMustBeInForeground() && !mDelegate.isChromeAppInForeground()) {
             return OverrideUrlLoadingResult.NO_OVERRIDE;
         }
         // http://crbug.com/464669 : Disallow firing external intent from background tab.
         if (params.isBackgroundTabNavigation()) {
             return OverrideUrlLoadingResult.NO_OVERRIDE;
         }
 
+        // http://crbug.com/605302 : Allow Chrome to handle all pdf file downloads.
+        if (mDelegate.isPdfDownload(params.getUrl())) {
+            return OverrideUrlLoadingResult.NO_OVERRIDE;
+        }
+
         // pageTransition is a combination of an enumeration (core value) and bitmask.
         int pageTransitionCore = params.getPageTransition() & PageTransition.CORE_MASK;
         boolean isLink = pageTransitionCore == PageTransition.LINK;
         boolean isFormSubmit = pageTransitionCore == PageTransition.FORM_SUBMIT;
         boolean isFromIntent = (params.getPageTransition() & PageTransition.FROM_API) != 0;
         boolean isForwardBackNavigation =
                 (params.getPageTransition() & PageTransition.FORWARD_BACK) != 0;
         boolean isExternalProtocol = !UrlUtilities.isAcceptedScheme(params.getUrl());
 
         // http://crbug.com/169549 : If you type in a URL that then redirects in server side to an
@@ skipping 307 matching lines @@
         if (defaultSmsPackageName == null) return null;
         // Makes sure that the default SMS app actually resolves the intent.
         for (ResolveInfo resolveInfo : resolvingComponentNames) {
             if (defaultSmsPackageName.equals(resolveInfo.activityInfo.packageName)) {
                 return defaultSmsPackageName;
             }
         }
         return null;
     }
 }