diff --git a/components/remote_cocoa/app_shim/select_file_dialog_bridge.mm b/components/remote_cocoa/app_shim/select_file_dialog_bridge.mm
index 306ae9656a4c0c..a1a6a83779a9e9 100644
--- a/components/remote_cocoa/app_shim/select_file_dialog_bridge.mm
+++ b/components/remote_cocoa/app_shim/select_file_dialog_bridge.mm
@@ -28,6 +28,14 @@
 
 const int kFileTypePopupTag = 1234;
 
+// TODO(macOS 11): Remove this.
+CFStringRef CreateUTIFromExtension(const base::FilePath::StringType& ext) {
+  base::apple::ScopedCFTypeRef<CFStringRef> ext_cf(
+      base::SysUTF8ToCFStringRef(ext));
+  return UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension,
+                                               ext_cf.get(), nullptr);
+}
+
 NSString* GetDescriptionFromExtension(const base::FilePath::StringType& ext) {
   if (@available(macOS 11, *)) {
     UTType* type =
@@ -38,12 +46,7 @@
       return description;
     }
   } else {
-    base::apple::ScopedCFTypeRef<CFStringRef> ext_cf =
-        base::SysUTF8ToCFStringRef(ext);
-    base::apple::ScopedCFTypeRef<CFStringRef> uti(
-        UTTypeCreatePreferredIdentifierForTag(kUTTagClassFilenameExtension,
-                                              ext_cf.get(),
-                                              /*inConformingToUTI=*/nullptr));
+    base::apple::ScopedCFTypeRef<CFStringRef> uti(CreateUTIFromExtension(ext));
     NSString* description =
         base::apple::CFToNSOwnershipCast(UTTypeCopyDescription(uti.get()));
 
@@ -216,47 +219,6 @@ - (BOOL)panel:(id)sender validateURL:(NSURL*)url error:(NSError**)outError {
   return YES;
 }
 
-- (BOOL)panel:(id)sender shouldEnableURL:(NSURL*)url {
-  // When provided UTTypes, NSOpenPanel determines whether files are selectable
-  // by conformance, not by strict type equality. For example, with
-  // public.plain-text, not only .txt files will be selectable, but .js, .m3u,
-  // and .csv files will be as well. With public.zip-archive, not only .zip
-  // files will be selectable, but also .jar files and .xlsb files.
-  //
-  // While this can be great for normal viewing/editing apps, this is not
-  // desirable for Chromium, where the web platform requires strict type
-  // matching on the provided extensions, and files that have a conforming file
-  // type by accident of their implementation shouldn't qualify for selection.
-  //
-  // Unfortunately, there's no great way to do strict type matching with
-  // NSOpenPanel. Setting explicit extensions via -allowedFileTypes is
-  // deprecated, and there's no way to specify that strict type equality should
-  // be used for -allowedContentTypes (FB13721802). Therefore, as inefficient as
-  // it is, this use of the delegate is required.
-
-  if (@available(macOS 11, *)) {
-    NSArray<UTType*>* allowedTypes = [sender allowedContentTypes];
-    if (!allowedTypes.count) {
-      // An empty array is "all types";
-      return YES;
-    }
-
-    UTType* type;
-    if (![url getResourceValue:&type forKey:NSURLContentTypeKey error:nil]) {
-      return NO;
-    }
-
-    return [allowedTypes containsObject:type];
-  } else {
-    // It is not documented, but -panel:shouldEnableURL: is a filter. Files for
-    // which NO is returned are disabled, but files for which YES is returned
-    // are further processed and filtered by the specified allowedFileTypes.
-    // Return YES and allow the further filtering by the file types already
-    // specified.
-    return YES;
-  }
-}
-
 @end
 
 @implementation ExtensionDropdownHandler
@@ -528,10 +490,21 @@ - (void)popupAction:(id)sender {
           [file_uttype_array addObject:type];
         }
       } else {
-        // Do not include any UTIs in this file type list. UTIs, if included,
-        // are compared with conformance, while strict type equality is
-        // required. See the -panel:shouldEnableURL: delegate callback above for
-        // more information.
+        // Crash reports suggest that CreateUTIFromExtension may return nil.
+        // Hence we nil check before adding to |file_type_set|. See
+        // crbug.com/630101 and rdar://27490414.
+        NSString* uti =
+            base::apple::CFToNSOwnershipCast(CreateUTIFromExtension(ext));
+        if (uti) {
+          if (![file_type_array containsObject:uti]) {
+            [file_type_array addObject:uti];
+          }
+        }
+
+        // Always allow the extension itself, in case the UTI doesn't map
+        // back to the original extension correctly. This occurs with dynamic
+        // UTIs on 10.7 and 10.8.
+        // See https://crbug.com/148840, https://openradar.appspot.com/12316273
         NSString* ext_ns = base::SysUTF8ToNSString(ext);
         if (![file_type_array containsObject:ext_ns]) {
           [file_type_array addObject:ext_ns];