Added support for improvement_direction to relevant values, which is propogated to chartjson.

tools/perf/benchmarks/indexeddb_perf.py

Index: tools/perf/benchmarks/indexeddb_perf.py
diff --git a/tools/perf/benchmarks/indexeddb_perf.py b/tools/perf/benchmarks/indexeddb_perf.py
index d6344df9204d781117f5c84989642f04bc1d21d9..1df6ec5ad88b7cdee19926b71234af5363092079 100644
--- a/tools/perf/benchmarks/indexeddb_perf.py
+++ b/tools/perf/benchmarks/indexeddb_perf.py
@@ -79,11 +79,13 @@ class _IndexedDbMeasurement(page_test.PageTest):
         continue
       msec = float(result_dict[key])
       results.AddValue(scalar.ScalarValue(
-          results.current_page, key, 'ms', msec, important=False))
+          results.current_page, key, 'ms', msec, important=False,
+          higher_is_better=False))
 
       total += msec
     results.AddValue(scalar.ScalarValue(
-        results.current_page, 'Total Perf', 'ms', total))
+        results.current_page, 'Total Perf', 'ms', total,
+        higher_is_better=False))
 
 
   def CustomizeBrowserOptions(self, options):