Move the trace sorting from the JS up to the Python, matching what's done for...

tools/buildbot/perf/dashboard/ui/generic_plotter.html

Index: tools/buildbot/perf/dashboard/ui/generic_plotter.html
===================================================================
--- tools/buildbot/perf/dashboard/ui/generic_plotter.html	(revision 10156)
+++ tools/buildbot/perf/dashboard/ui/generic_plotter.html	(working copy)
@@ -190,58 +190,13 @@
       allTraces[traceName] = 1;
   }
 
-  // Sort trace names, putting traces with corresponding _ref lines first
-  // under the assumption that those are the most interesting ones.
-  // Returns 1 if name1 is larger, -1 if it's smaller, and 0 if they're equal.
-  // Use a closure so we have access to allTraces.
-  function trace_compare(name1, name2) {
-    function compare(x, y) {
-      return ((x < y) ? -1 : (x > y) ? 1 : 0);
-    }
-
-    // The main trace name associated with this _ref name, and whether this is
-    // in fact a _ref trace.
-    main1 = name1.substring(0, name1.length - 4);
-    main2 = name2.substring(0, name2.length - 4);
-    is_ref1 = name1.substr(-4) == "_ref" && main1 in allTraces;
-    is_ref2 = name2.substr(-4) == "_ref" && main2 in allTraces;
-
-    // Whether this trace has a corresponding _ref. If so, it's its own main
-    // trace.
-    is_main1 = name1 + "_ref" in allTraces;
-    is_main2 = name2 + "_ref" in allTraces;
-    if (is_main1)
-      main1 = name1;
-    if (is_main2)
-      main2 = name2;
-
-    // A main trace is smaller than its own _ref, compared alphabetically by
-    // main name to any other main or _ref traces, and smaller than anything
-    // else.
-    if (is_main1) {
-      if (is_ref2 && main1 == main2)
-        return -1;
-      if (is_main2 || is_ref2)
-        return compare(main1, main2);
-      return -1;
-    }
-    if (is_ref1) {
-      if (is_main2 && main1 == main2)
-        return 1;
-      if (is_main2 || is_ref2)
-        return compare(main1, main2);
-      return -1;
-    }
-    if (is_main2 || is_ref2)
-      return 1;
-    return compare(name1, name2);
-  }
-
-  // Build and sort a list of all the trace names we've seen.
+  // Build a list of all the trace names we've seen, in the order in which
+  // they appear in the data file. Although JS objects are not required by
+  // the spec to iterate their properties in order, in practice they do,
+  // because it causes compatibility problems otherwise.
   var traceNames = [];
   for (var traceName in allTraces)
     traceNames.push(traceName);
-  traceNames.sort(trace_compare);
 
   // Build and numerically sort a list of revision numbers.
   var revisionNumbers = [];