diff --git a/docshell/base/nsWebNavigationInfo.cpp b/docshell/base/nsWebNavigationInfo.cpp
index 9b7aa55dbe..0eb4f49070 100644
--- a/docshell/base/nsWebNavigationInfo.cpp
+++ b/docshell/base/nsWebNavigationInfo.cpp
@@ -44,13 +44,6 @@ nsWebNavigationInfo::IsTypeSupported(const nsACString& aType,
   // to say for itself.
   *aIsTypeSupported = nsIWebNavigationInfo::UNSUPPORTED;
 
-  // We want to claim that the type for PDF documents is unsupported,
-  // so that the internal PDF viewer's stream converted will get used.
-  if (aType.LowerCaseEqualsLiteral("application/pdf") &&
-      nsContentUtils::IsPDFJSEnabled()) {
-    return NS_OK;
-  }
-
   const nsCString& flatType = PromiseFlatCString(aType);
   nsresult rv = IsTypeSupportedInternal(flatType, aIsTypeSupported);
   NS_ENSURE_SUCCESS(rv, rv);
diff --git a/dom/base/nsContentUtils.cpp b/dom/base/nsContentUtils.cpp
index 6199fc5884..3f3b7c4fc8 100644
--- a/dom/base/nsContentUtils.cpp
+++ b/dom/base/nsContentUtils.cpp
@@ -6406,19 +6406,6 @@ nsContentUtils::AllowXULXBLForPrincipal(nsIPrincipal* aPrincipal)
           IsSitePermAllow(aPrincipal, "allowXULXBL"));
 }
 
-bool
-nsContentUtils::IsPDFJSEnabled()
-{
-   nsCOMPtr<nsIStreamConverterService> convServ =
-     do_GetService("@mozilla.org/streamConverters;1");
-   nsresult rv = NS_ERROR_FAILURE;
-   bool canConvert = false;
-   if (convServ) {
-     rv = convServ->CanConvert("application/pdf", "text/html", &canConvert);
-   }
-   return NS_SUCCEEDED(rv) && canConvert;
-}
-
 already_AddRefed<nsIDocumentLoaderFactory>
 nsContentUtils::FindInternalContentViewer(const char* aType,
                                           ContentViewerType* aLoaderType)
diff --git a/dom/base/nsContentUtils.h b/dom/base/nsContentUtils.h
index 84511a0d24..58d219970a 100644
--- a/dom/base/nsContentUtils.h
+++ b/dom/base/nsContentUtils.h
@@ -2011,11 +2011,6 @@ public:
    */
   static void XPCOMShutdown();
 
-  /**
-   * Checks if internal PDF viewer is enabled.
-   */
-  static bool IsPDFJSEnabled();
-
   enum ContentViewerType
   {
       TYPE_UNSUPPORTED,
diff --git a/dom/base/nsObjectLoadingContent.cpp b/dom/base/nsObjectLoadingContent.cpp
index 0eda9795c7..7b6d21b275 100644
--- a/dom/base/nsObjectLoadingContent.cpp
+++ b/dom/base/nsObjectLoadingContent.cpp
@@ -552,11 +552,6 @@ IsPluginEnabledByExtension(nsIURI* uri, nsCString& mimeType)
     return false;
   }
 
-  // Disables any native PDF plugins, when internal PDF viewer is enabled.
-  if (ext.EqualsIgnoreCase("pdf") && nsContentUtils::IsPDFJSEnabled()) {
-    return false;
-  }
-
   nsRefPtr<nsPluginHost> pluginHost = nsPluginHost::GetInst();
 
   if (!pluginHost) {
@@ -2674,13 +2669,6 @@ nsObjectLoadingContent::GetTypeOfContent(const nsCString& aMIMEType)
     return eType_Image;
   }
 
-  // Faking support of the PDF content as a document for EMBED tags
-  // when internal PDF viewer is enabled.
-  if (aMIMEType.LowerCaseEqualsLiteral("application/pdf") &&
-      nsContentUtils::IsPDFJSEnabled()) {
-    return eType_Document;
-  }
-
   // SVGs load as documents, but are their own capability
   bool isSVG = aMIMEType.LowerCaseEqualsLiteral("image/svg+xml");
   Capabilities supportType = isSVG ? eSupportSVG : eSupportDocuments;
diff --git a/python/mozbuild/mozpack/test/test_chrome_manifest.py b/python/mozbuild/mozpack/test/test_chrome_manifest.py
index 4f8bc8a373..2c72ae178d 100644
--- a/python/mozbuild/mozpack/test/test_chrome_manifest.py
+++ b/python/mozbuild/mozpack/test/test_chrome_manifest.py
@@ -39,7 +39,6 @@ class TestManifest(unittest.TestCase):
             'skin global classic/1.0 content/skin/classic/ application=foo' +
             ' os=WINNT',
             '',
-            'manifest pdfjs/chrome.manifest',
             'resource gre-resources toolkit/res/',
             'override chrome://global/locale/netError.dtd' +
             ' chrome://browser/locale/netError.dtd',
@@ -70,7 +69,6 @@ class TestManifest(unittest.TestCase):
             ManifestSkin('', 'global', 'classic/1.0', 'content/skin/classic/'),
             ManifestSkin('', 'global', 'classic/1.0', 'content/skin/classic/',
                          'application=foo', 'os=WINNT'),
-            Manifest('', 'pdfjs/chrome.manifest'),
             ManifestResource('', 'gre-resources', 'toolkit/res/'),
             ManifestOverride('', 'chrome://global/locale/netError.dtd',
                              'chrome://browser/locale/netError.dtd'),
diff --git a/python/mozbuild/mozpack/test/test_files.py b/python/mozbuild/mozpack/test/test_files.py
index 99bd40b5ed..422143c294 100644
--- a/python/mozbuild/mozpack/test/test_files.py
+++ b/python/mozbuild/mozpack/test/test_files.py
@@ -611,8 +611,6 @@ class TestManifestFile(TestWithTmpDir):
         f = ManifestFile('chrome')
         f.add(ManifestContent('chrome', 'global', 'toolkit/content/global/'))
         f.add(ManifestResource('chrome', 'gre-resources', 'toolkit/res/'))
-        f.add(ManifestResource('chrome/pdfjs', 'pdfjs', './'))
-        f.add(ManifestContent('chrome/pdfjs', 'pdfjs', 'pdfjs'))
         f.add(ManifestLocale('chrome', 'browser', 'en-US',
                              'en-US/locale/browser/'))
 
@@ -620,8 +618,6 @@ class TestManifestFile(TestWithTmpDir):
         self.assertEqual(open(self.tmppath('chrome.manifest')).readlines(), [
             'content global toolkit/content/global/\n',
             'resource gre-resources toolkit/res/\n',
-            'resource pdfjs pdfjs/\n',
-            'content pdfjs pdfjs/pdfjs\n',
             'locale browser en-US en-US/locale/browser/\n',
         ])