Fix a bug in file name sorting

This fix addresses a typo in filename sorting.

Bug: Issue 4448
Change-Id: I5d5a74c74850f5f745949388387138f573602bd4
diff --git a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js
index 0b07217..19a405c 100644
--- a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js
+++ b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface.js
@@ -426,7 +426,7 @@
 
       var bLastDotIndex = b.lastIndexOf('.');
       var bExt = b.substr(bLastDotIndex + 1);
-      var bFile = a.substr(0, bLastDotIndex);
+      var bFile = b.substr(0, bLastDotIndex);
 
       // Sort header files above others with the same base name.
       var headerExts = ['h', 'hxx', 'hpp'];
diff --git a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface_test.html b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface_test.html
index 8dda2ce..2481b1f 100644
--- a/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface_test.html
+++ b/polygerrit-ui/app/elements/shared/gr-rest-api-interface/gr-rest-api-interface_test.html
@@ -237,6 +237,21 @@
           ['foo/bar.h', 'foo/bar.hxx', 'foo/bar.hpp'].sort(
               element._specialFilePathCompare),
           ['foo/bar.h', 'foo/bar.hpp', 'foo/bar.hxx']);
+
+      // Regression test for Issue 4448.
+      assert.deepEqual([
+          'minidump/minidump_memory_writer.cc',
+          'minidump/minidump_memory_writer.h',
+          'minidump/minidump_thread_writer.cc',
+          'minidump/minidump_thread_writer.h',
+          ]
+        .sort(element._specialFilePathCompare),
+          [
+            'minidump/minidump_memory_writer.h',
+            'minidump/minidump_memory_writer.cc',
+            'minidump/minidump_thread_writer.h',
+            'minidump/minidump_thread_writer.cc',
+          ]);
     });
 
     test('rebase always enabled', function(done) {