diff --git a/extensions/chromium/contentscript.js b/extensions/chromium/contentscript.js
index 1e596c493..aa6edb7b3 100644
--- a/extensions/chromium/contentscript.js
+++ b/extensions/chromium/contentscript.js
@@ -22,11 +22,7 @@ function getViewerURL(pdf_url) {
   return VIEWER_URL + "?file=" + encodeURIComponent(pdf_url);
 }
 
-if (CSS.supports("animation", "0s")) {
-  document.addEventListener("animationstart", onAnimationStart, true);
-} else {
-  document.addEventListener("webkitAnimationStart", onAnimationStart, true);
-}
+document.addEventListener("animationstart", onAnimationStart, true);
 
 function onAnimationStart(event) {
   if (event.animationName === "pdfjs-detected-object-or-embed") {
diff --git a/extensions/chromium/contentstyle.css b/extensions/chromium/contentstyle.css
index 5829b0682..4d8f8ba86 100644
--- a/extensions/chromium/contentstyle.css
+++ b/extensions/chromium/contentstyle.css
@@ -1,11 +1,6 @@
 /**
  * Detect creation of <embed> and <object> tags.
  */
-@-webkit-keyframes pdfjs-detected-object-or-embed {
-  from {
-    /* empty */
-  }
-}
 @keyframes pdfjs-detected-object-or-embed {
   from {
     /* empty */
@@ -13,9 +8,6 @@
 }
 object,
 embed {
-  -webkit-animation-delay: 0s !important;
-  -webkit-animation-name: pdfjs-detected-object-or-embed !important;
-  -webkit-animation-play-state: running !important;
   animation-delay: 0s !important;
   animation-name: pdfjs-detected-object-or-embed !important;
   animation-play-state: running !important;
diff --git a/extensions/chromium/pdfHandler.js b/extensions/chromium/pdfHandler.js
index 3b014db5c..95e150051 100644
--- a/extensions/chromium/pdfHandler.js
+++ b/extensions/chromium/pdfHandler.js
@@ -154,19 +154,7 @@ chrome.webRequest.onBeforeRequest.addListener(
     return { redirectUrl: viewerUrl };
   },
   {
-    urls: [
-      "file://*/*.pdf",
-      "file://*/*.PDF",
-      ...// Duck-typing: MediaError.prototype.message was added in Chrome 59.
-      (MediaError.prototype.hasOwnProperty("message")
-        ? []
-        : [
-            // Note: Chrome 59 has disabled ftp resource loading by default:
-            // https://www.chromestatus.com/feature/5709390967472128
-            "ftp://*/*.pdf",
-            "ftp://*/*.PDF",
-          ]),
-    ],
+    urls: ["file://*/*.pdf", "file://*/*.PDF"],
     types: ["main_frame", "sub_frame"],
   },
   ["blocking"]
@@ -252,10 +240,3 @@ chrome.runtime.onMessage.addListener(function (message, sender, sendResponse) {
   }
   return undefined;
 });
-
-// Remove keys from storage that were once part of the deleted feature-detect.js
-chrome.storage.local.remove([
-  "featureDetectLastUA",
-  "webRequestRedirectUrl",
-  "extensionSupportsFTP",
-]);
diff --git a/extensions/chromium/preserve-referer.js b/extensions/chromium/preserve-referer.js
index cef150cd4..97a99e063 100644
--- a/extensions/chromium/preserve-referer.js
+++ b/extensions/chromium/preserve-referer.js
@@ -42,30 +42,18 @@ var g_requestHeaders = {};
 // g_referrers[tabId][frameId] = referrer of PDF frame.
 var g_referrers = {};
 
-var extraInfoSpecWithHeaders; // = ['requestHeaders', 'extraHeaders']
-
 (function () {
   var requestFilter = {
     urls: ["*://*/*"],
     types: ["main_frame", "sub_frame"],
   };
-  function registerListener(extraInfoSpec) {
-    extraInfoSpecWithHeaders = extraInfoSpec;
-    // May throw if the given extraInfoSpec is unsupported.
-    chrome.webRequest.onSendHeaders.addListener(
-      function (details) {
-        g_requestHeaders[details.requestId] = details.requestHeaders;
-      },
-      requestFilter,
-      extraInfoSpec
-    );
-  }
-  try {
-    registerListener(["requestHeaders", "extraHeaders"]);
-  } catch {
-    // "extraHeaders" is not supported in Chrome 71 and earlier.
-    registerListener(["requestHeaders"]);
-  }
+  chrome.webRequest.onSendHeaders.addListener(
+    function (details) {
+      g_requestHeaders[details.requestId] = details.requestHeaders;
+    },
+    requestFilter,
+    ["requestHeaders", "extraHeaders"]
+  );
   chrome.webRequest.onBeforeRedirect.addListener(forgetHeaders, requestFilter);
   chrome.webRequest.onCompleted.addListener(forgetHeaders, requestFilter);
   chrome.webRequest.onErrorOccurred.addListener(forgetHeaders, requestFilter);
@@ -126,7 +114,7 @@ chrome.runtime.onConnect.addListener(function onReceivePort(port) {
           types: ["xmlhttprequest"],
           tabId,
         },
-        ["blocking", ...extraInfoSpecWithHeaders]
+        ["blocking", "requestHeaders", "extraHeaders"]
       );
     }
     // Acknowledge the message, and include the latest referer for this frame.
diff --git a/extensions/chromium/telemetry.js b/extensions/chromium/telemetry.js
index a142a19aa..7a985e3a1 100644
--- a/extensions/chromium/telemetry.js
+++ b/extensions/chromium/telemetry.js
@@ -70,29 +70,20 @@ limitations under the License.
 
       var deduplication_id = getDeduplicationId(wasUpdated);
       var extension_version = chrome.runtime.getManifest().version;
-      if (window.Request && "mode" in Request.prototype) {
-        // fetch is supported in extensions since Chrome 42 (though the above
-        // feature-detection method detects Chrome 43+).
-        // Unlike XMLHttpRequest, fetch omits credentials such as cookies in the
-        // requests, which guarantees that the server cannot track the client
-        // via HTTP cookies.
-        fetch(LOG_URL, {
-          method: "POST",
-          headers: new Headers({
-            "Deduplication-Id": deduplication_id,
-            "Extension-Version": extension_version,
-          }),
-          // Set mode=cors so that the above custom headers are included in the
-          // request.
-          mode: "cors",
-        });
-        return;
-      }
-      var x = new XMLHttpRequest();
-      x.open("POST", LOG_URL);
-      x.setRequestHeader("Deduplication-Id", deduplication_id);
-      x.setRequestHeader("Extension-Version", extension_version);
-      x.send();
+      fetch(LOG_URL, {
+        method: "POST",
+        headers: new Headers({
+          "Deduplication-Id": deduplication_id,
+          "Extension-Version": extension_version,
+        }),
+        // Set mode=cors so that the above custom headers are included in the
+        // request.
+        mode: "cors",
+        // Omits credentials such as cookies in the requests, which guarantees
+        // that the server cannot track the client via HTTP cookies.
+        credentials: "omit",
+        cache: "no-store",
+      });
     });
   }