diff --git a/extensions/chromium/feature-detect.js b/extensions/chromium/feature-detect.js
deleted file mode 100644
index 91cfc90b8fd95..0000000000000
--- a/extensions/chromium/feature-detect.js
+++ /dev/null
@@ -1,125 +0,0 @@
-/*
-Copyright 2014 Mozilla Foundation
-
-Licensed under the Apache License, Version 2.0 (the "License");
-you may not use this file except in compliance with the License.
-You may obtain a copy of the License at
-
-    http://www.apache.org/licenses/LICENSE-2.0
-
-Unless required by applicable law or agreed to in writing, software
-distributed under the License is distributed on an "AS IS" BASIS,
-WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-See the License for the specific language governing permissions and
-limitations under the License.
-*/
-
-'use strict';
-
-var Features = {
-  featureDetectLastUA: '',
-  // Whether ftp: in XMLHttpRequest is allowed
-  extensionSupportsFTP: false,
-  // Whether redirectUrl at onHeadersReceived is supported.
-  webRequestRedirectUrl: false,
-};
-
-chrome.storage.local.get(Features, function(features) {
-  Features = features;
-  if (features.featureDetectLastUA === navigator.userAgent) {
-    // Browser not upgraded, so the features did probably not change.
-    return;
-  }
-
-  // In case of a downgrade, the features must be tested again.
-  var lastVersion = /Chrome\/\d+\.0\.(\d+)/.exec(features.featureDetectLastUA);
-  lastVersion = lastVersion ? parseInt(lastVersion[1], 10) : 0;
-  var newVersion = /Chrome\/\d+\.0\.(\d+)/.exec(navigator.userAgent);
-  var isDowngrade = newVersion && parseInt(newVersion[1], 10) < lastVersion;
-
-  var inconclusiveTestCount = 0;
-
-  if (isDowngrade || !features.extensionSupportsFTP) {
-    features.extensionSupportsFTP = featureTestFTP();
-  }
-
-  if (isDowngrade || !features.webRequestRedirectUrl) {
-    ++inconclusiveTestCount;
-    // Relatively expensive (and asynchronous) test:
-    featureTestRedirectOnHeadersReceived(function(result) {
-      // result = 'yes', 'no' or 'maybe'.
-      if (result !== 'maybe') {
-        --inconclusiveTestCount;
-      }
-      features.webRequestRedirectUrl = result === 'yes';
-      checkTestCompletion();
-    });
-  }
-
-  checkTestCompletion();
-
-  function checkTestCompletion() {
-    // Only stamp the feature detection results when all tests have finished.
-    if (inconclusiveTestCount === 0) {
-      Features.featureDetectLastUA = navigator.userAgent;
-    }
-    chrome.storage.local.set(Features);
-  }
-});
-
-// Tests whether the extension can perform a FTP request.
-// Feature is supported since Chromium 35.0.1888.0 (r256810).
-function featureTestFTP() {
-  var x = new XMLHttpRequest();
-  // The URL does not need to exist, as long as the scheme is ftp:.
-  x.open('GET', 'ftp://ftp.mozilla.org/');
-  try {
-    x.send();
-    // Previous call did not throw error, so the feature is supported!
-    // Immediately abort the request so that the network is not hit at all.
-    x.abort();
-    return true;
-  } catch (e) {
-    return false;
-  }
-}
-
-// Tests whether redirectUrl at the onHeadersReceived stage is functional.
-// Feature is supported since Chromium 35.0.1911.0 (r259546).
-function featureTestRedirectOnHeadersReceived(callback) {
-  // The following URL is really going to be accessed via the network.
-  // It is the only way to feature-detect this feature, because the
-  // onHeadersReceived event is only triggered for http(s) requests.
-  var url = 'http://example.com/?feature-detect-' + chrome.runtime.id;
-  function onHeadersReceived(details) {
-    // If supported, the request is redirected.
-    // If not supported, the return value is ignored.
-    return {
-      redirectUrl: chrome.runtime.getURL('/manifest.json'),
-    };
-  }
-  chrome.webRequest.onHeadersReceived.addListener(onHeadersReceived, {
-    types: ['xmlhttprequest'],
-    urls: [url],
-  }, ['blocking']);
-
-  var x = new XMLHttpRequest();
-  x.open('get', url);
-  x.onloadend = function() {
-    chrome.webRequest.onHeadersReceived.removeListener(onHeadersReceived);
-    if (!x.responseText) {
-      // Network error? Anyway, can't tell with certainty whether the feature
-      // is supported.
-      callback('maybe');
-    } else if (/^\s*\{/.test(x.responseText)) {
-      // If the response starts with "{", assume that the redirection to the
-      // manifest file succeeded, so the feature is supported.
-      callback('yes');
-    } else {
-      // Did not get the content of manifest.json, so the redirect seems not to
-      // be followed. The feature is not supported.
-      callback('no');
-    }
-  };
-  x.send();
-}
diff --git a/extensions/chromium/pdfHandler.html b/extensions/chromium/pdfHandler.html
index 728a038c3a0e0..a87cec438786f 100644
--- a/extensions/chromium/pdfHandler.html
+++ b/extensions/chromium/pdfHandler.html
@@ -14,7 +14,6 @@
 See the License for the specific language governing permissions and
 limitations under the License.
 -->
-<script src="feature-detect.js"></script>
 <script src="options/migration.js"></script>
 <script src="preserve-referer.js"></script>
 <script src="pdfHandler.js"></script>
diff --git a/extensions/chromium/pdfHandler.js b/extensions/chromium/pdfHandler.js
index 5dac71546a6c5..b22c98afe3fd0 100644
--- a/extensions/chromium/pdfHandler.js
+++ b/extensions/chromium/pdfHandler.js
@@ -13,7 +13,6 @@ WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */
-/* import-globals-from feature-detect.js */
 /* import-globals-from preserve-referer.js */
 
 'use strict';
@@ -131,21 +130,7 @@ chrome.webRequest.onHeadersReceived.addListener(
     // Implemented in preserve-referer.js
     saveReferer(details);
 
-    // Replace frame with viewer
-    if (Features.webRequestRedirectUrl) {
-      return { redirectUrl: viewerUrl, };
-    }
-    // Aww.. redirectUrl is not yet supported, so we have to use a different
-    // method as fallback (Chromium <35).
-
-    if (details.frameId === 0) {
-      // Main frame. Just replace the tab and be done!
-      chrome.tabs.update(details.tabId, {
-        url: viewerUrl,
-      });
-      return { cancel: true, };
-    }
-    console.warn('Child frames are not supported in ancient Chrome builds!');
+    return { redirectUrl: viewerUrl, };
   },
   {
     urls: [
@@ -155,36 +140,12 @@ chrome.webRequest.onHeadersReceived.addListener(
   },
   ['blocking', 'responseHeaders']);
 
-chrome.webRequest.onBeforeRequest.addListener(
-  function onBeforeRequestForFTP(details) {
-    if (!Features.extensionSupportsFTP) {
-      chrome.webRequest.onBeforeRequest.removeListener(onBeforeRequestForFTP);
-      return;
-    }
-    if (isPdfDownloadable(details)) {
-      return;
-    }
-    var viewerUrl = getViewerURL(details.url);
-    return { redirectUrl: viewerUrl, };
-  },
-  {
-    urls: [
-      'ftp://*/*.pdf',
-      'ftp://*/*.PDF'
-    ],
-    types: ['main_frame', 'sub_frame'],
-  },
-  ['blocking']);
-
 chrome.webRequest.onBeforeRequest.addListener(
   function(details) {
     if (isPdfDownloadable(details)) {
       return;
     }
 
-    // NOTE: The manifest file has declared an empty content script
-    // at file://*/* to make sure that the viewer can load the PDF file
-    // through XMLHttpRequest. Necessary to deal with http://crbug.com/302548
     var viewerUrl = getViewerURL(details.url);
 
     return { redirectUrl: viewerUrl, };
@@ -192,7 +153,11 @@ chrome.webRequest.onBeforeRequest.addListener(
   {
     urls: [
       'file://*/*.pdf',
-      'file://*/*.PDF'
+      'file://*/*.PDF',
+      // Note: Chrome 59 has disabled ftp resource loading by default:
+      // https://www.chromestatus.com/feature/5709390967472128
+      'ftp://*/*.pdf',
+      'ftp://*/*.PDF',
     ],
     types: ['main_frame', 'sub_frame'],
   },
@@ -271,3 +236,10 @@ chrome.runtime.onMessage.addListener(function(message, sender, sendResponse) {
     }
   }
 });
+
+// Remove keys from storage that were once part of the deleted feature-detect.js
+chrome.storage.local.remove([
+  'featureDetectLastUA',
+  'webRequestRedirectUrl',
+  'extensionSupportsFTP',
+]);
diff --git a/web/chromecom.js b/web/chromecom.js
index 6ec8ed84a077e..9afeab5380469 100644
--- a/web/chromecom.js
+++ b/web/chromecom.js
@@ -18,7 +18,6 @@ import { DefaultExternalServices, PDFViewerApplication } from './app';
 import { BasePreferences } from './preferences';
 import { DownloadManager } from './download_manager';
 import { GenericL10n } from './genericl10n';
-import { PDFJS } from 'pdfjs-lib';
 
 if (typeof PDFJSDev === 'undefined' || !PDFJSDev.test('CHROME')) {
   throw new Error('Module "pdfjs-web/chromecom" shall not be used outside ' +
@@ -65,26 +64,6 @@ let ChromeCom = {
     file = file.replace(/^drive:/i,
         'filesystem:' + location.origin + '/external/');
 
-    if (/^filesystem:/.test(file) && !PDFJS.disableWorker) {
-      // The security origin of filesystem:-URLs are not preserved when the
-      // URL is passed to a Web worker, (http://crbug.com/362061), so we have
-      // to create an intermediate blob:-URL as a work-around.
-      let resolveLocalFileSystemURL = window.resolveLocalFileSystemURL ||
-                                      window.webkitResolveLocalFileSystemURL;
-      resolveLocalFileSystemURL(file, function onResolvedFSURL(fileEntry) {
-        fileEntry.file(function(fileObject) {
-          let blobUrl = URL.createObjectURL(fileObject);
-          callback(blobUrl, fileObject.size);
-        });
-      }, function onFileSystemError(error) {
-        // This should not happen. When it happens, just fall back to the
-        // usual way of getting the File's data (via the Web worker).
-        console.warn('Cannot resolve file ' + file + ', ' + error.name + ' ' +
-                     error.message);
-        callback(file);
-      });
-      return;
-    }
     if (/^https?:/.test(file)) {
       // Assumption: The file being opened is the file that was requested.
       // There is no UI to input a different URL, so this assumption will hold
diff --git a/web/pdf_history.js b/web/pdf_history.js
index 5bdc17b92217f..3ca1df2cdb62d 100644
--- a/web/pdf_history.js
+++ b/web/pdf_history.js
@@ -281,23 +281,10 @@ class PDFHistory {
     this._updateInternalState(destination, newState.uid);
 
     if (shouldReplace) {
-      if (typeof PDFJSDev !== 'undefined' &&
-          PDFJSDev.test('FIREFOX || MOZCENTRAL')) {
-        // Providing the third argument causes a SecurityError for file:// URLs.
-        window.history.replaceState(newState, '');
-      } else {
-        window.history.replaceState(newState, '', document.URL);
-      }
+      window.history.replaceState(newState, '');
     } else {
       this._maxUid = this._uid;
-
-      if (typeof PDFJSDev !== 'undefined' &&
-          PDFJSDev.test('FIREFOX || MOZCENTRAL')) {
-        // Providing the third argument causes a SecurityError for file:// URLs.
-        window.history.pushState(newState, '');
-      } else {
-        window.history.pushState(newState, '', document.URL);
-      }
+      window.history.pushState(newState, '');
     }
 
     if (typeof PDFJSDev !== 'undefined' && PDFJSDev.test('CHROME') &&