diff --git a/browser/base/content/tabbrowser.js b/browser/base/content/tabbrowser.js
index e9836ba6df6a..0bbe0b0196fc 100644
--- a/browser/base/content/tabbrowser.js
+++ b/browser/base/content/tabbrowser.js
@@ -853,38 +853,6 @@
       return rv;
     },
 
-    /**
-     * Determine if a URI is an about: page pointing to a local resource.
-     */
-    isLocalAboutURI(aURI, aResolvedURI) {
-      if (!aURI.schemeIs("about")) {
-        return false;
-      }
-
-      // Specially handle about:blank as local
-      if (aURI.pathQueryRef === "blank") {
-        return true;
-      }
-
-      try {
-        // Use the passed in resolvedURI if we have one
-        const resolvedURI =
-          aResolvedURI ||
-          Services.io.newChannelFromURI(
-            aURI,
-            null, // loadingNode
-            Services.scriptSecurityManager.getSystemPrincipal(), // loadingPrincipal
-            null, // triggeringPrincipal
-            Ci.nsILoadInfo.SEC_ALLOW_CROSS_ORIGIN_DATA_IS_NULL, // securityFlags
-            Ci.nsIContentPolicy.TYPE_OTHER // contentPolicyType
-          ).URI;
-        return resolvedURI.schemeIs("jar") || resolvedURI.schemeIs("file");
-      } catch (ex) {
-        // aURI might be invalid.
-        return false;
-      }
-    },
-
     /**
      * Sets an icon for the tab if the URI is defined in FAVICON_DEFAULTS.
      */
@@ -5567,7 +5535,7 @@
       // pointing to local resources.
       if (
         aRequest instanceof Ci.nsIChannel &&
-        gBrowser.isLocalAboutURI(aRequest.originalURI, aRequest.URI)
+        aRequest.originalURI.schemeIs("about")
       ) {
         return false;
       }
diff --git a/browser/base/content/test/tabs/browser.ini b/browser/base/content/test/tabs/browser.ini
index 76a19a411639..71623bedf6e1 100644
--- a/browser/base/content/test/tabs/browser.ini
+++ b/browser/base/content/test/tabs/browser.ini
@@ -24,7 +24,6 @@ tags = audiochannel
 skip-if = (verify && debug && (os == 'linux'))
 support-files =
   test_bug1358314.html
-[browser_isLocalAboutURI.js]
 [browser_e10s_about_page_triggeringprincipal.js]
 skip-if = verify
 support-files =
diff --git a/browser/base/content/test/tabs/browser_isLocalAboutURI.js b/browser/base/content/test/tabs/browser_isLocalAboutURI.js
deleted file mode 100644
index eee28bd75661..000000000000
--- a/browser/base/content/test/tabs/browser_isLocalAboutURI.js
+++ /dev/null
@@ -1,56 +0,0 @@
-/* Any copyright is dedicated to the Public Domain.
- * http://creativecommons.org/publicdomain/zero/1.0/ */
-
-"use strict";
-
-/**
- * Unit tests for tabbrowser.isLocalAboutURI to make sure it returns the
- * appropriate values for various URIs as well as optional resolved URI.
- */
-
-add_task(function test_URI() {
-  const check = (spec, expect, description) => {
-    const URI = Services.io.newURI(spec);
-    try {
-      is(gBrowser.isLocalAboutURI(URI), expect, description);
-    } catch (ex) {
-      ok(false, "isLocalAboutURI should not throw");
-    }
-  };
-  check("https://www.mozilla.org/", false, "https is not about");
-  check("http://www.mozilla.org/", false, "http is not about");
-  check("about:blank", true, "about:blank is local");
-  check("about:about", true, "about:about is local");
-  check("about:newtab", true, "about:newtab is local");
-  check(
-    "about:random-invalid-uri",
-    false,
-    "about:random-invalid-uri is invalid but should not throw"
-  );
-});
-
-add_task(function test_URI_with_resolved() {
-  const check = (spec, resolvedSpec, expect, description) => {
-    const URI = Services.io.newURI(spec);
-    const resolvedURI = Services.io.newURI(resolvedSpec);
-    is(gBrowser.isLocalAboutURI(URI, resolvedURI), expect, description);
-  };
-  check(
-    "about:newtab",
-    "jar:file:///Applications/Firefox.app/Contents/Resources/browser/omni.ja!/chrome/browser/res/activity-stream/prerendered/en-US/activity-stream.html",
-    true,
-    "about:newtab with jar is local"
-  );
-  check(
-    "about:newtab",
-    "file:///mozilla-central/browser/base/content/newtab/newTab.xhtml",
-    true,
-    "about:newtab with file is local"
-  );
-  check(
-    "about:newtab",
-    "https://www.mozilla.org/newtab",
-    false,
-    "about:newtab with https is not local"
-  );
-});
diff --git a/browser/components/sessionstore/SessionStore.jsm b/browser/components/sessionstore/SessionStore.jsm
index db2cb05a7040..9d051d65d05a 100644
--- a/browser/components/sessionstore/SessionStore.jsm
+++ b/browser/components/sessionstore/SessionStore.jsm
@@ -2978,7 +2978,7 @@ var SessionStoreInternal = {
     // waiting for data from the frame script. This throbber is disabled
     // if the URI is a local about: URI.
     let uriObj = aTab.linkedBrowser.currentURI;
-    if (!uriObj || (uriObj && !aWindow.gBrowser.isLocalAboutURI(uriObj))) {
+    if (!uriObj || (uriObj && !uriObj.schemeIs("about"))) {
       newTab.setAttribute("busy", "true");
     }
 
@@ -3662,7 +3662,7 @@ var SessionStoreInternal = {
     // Start the throbber to pretend we're doing something while actually
     // waiting for data from the frame script. This throbber is disabled
     // if the URI is a local about: URI.
-    if (!uriObj || (uriObj && !window.gBrowser.isLocalAboutURI(uriObj))) {
+    if (!uriObj || (uriObj && !uriObj.schemeIs("about"))) {
       tab.setAttribute("busy", "true");
     }
 
diff --git a/browser/modules/AsyncTabSwitcher.jsm b/browser/modules/AsyncTabSwitcher.jsm
index 5ab93207e1cc..d902e5c430a2 100644
--- a/browser/modules/AsyncTabSwitcher.jsm
+++ b/browser/modules/AsyncTabSwitcher.jsm
@@ -374,9 +374,7 @@ class AsyncTabSwitcher {
       // determined by the busy state on the tab element and checking
       // if the loaded URI is local.
       let isBusy = this.requestedTab.hasAttribute("busy");
-      let isLocalAbout = this.tabbrowser.isLocalAboutURI(
-        requestedBrowser.currentURI
-      );
+      let isLocalAbout = requestedBrowser.currentURI.schemeIs("about");
       let hasSufficientlyLoaded = !isBusy && !isLocalAbout;
 
       let fl = requestedBrowser.frameLoader;