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

tools/telemetry/telemetry/value/value_unittest.py

Index: tools/telemetry/telemetry/value/value_unittest.py
diff --git a/tools/telemetry/telemetry/value/value_unittest.py b/tools/telemetry/telemetry/value/value_unittest.py
index 69e48d918c181b07f356c63a1445002fa18bab49..b793dfc0143e5f286b7eea98d18d3a7d8b86a39b 100644
--- a/tools/telemetry/telemetry/value/value_unittest.py
+++ b/tools/telemetry/telemetry/value/value_unittest.py
@@ -92,14 +92,17 @@ class ValueTest(TestBase):
     self.assertFalse(b.IsMergableWith(a))
 
   def testAsDictBaseKeys(self):
-    v = ValueForAsDictTest(None, 'x', 'unit', important=True, description=None)
+    v = ValueForAsDictTest(
+        None, 'x', 'unit', important=True, description=None,
+        higher_is_better=True)
     d = v.AsDict()
 
     self.assertEquals(d, {
           'name': 'x',
           'type': 'baz',
           'units': 'unit',
-          'important': True
+          'important': True,
+          'higher_is_better': True,
         })
 
   def testAsDictWithPage(self):
@@ -131,13 +134,15 @@ class ValueTest(TestBase):
     d = {
       'type': 'value_for_from_dict_test',
       'name': 'x',
-      'units': 'unit'
+      'units': 'unit',
+      'higher_is_better': True
     }
 
     v = value.Value.FromDict(d, None)
     self.assertEquals(v.name, 'x')
     self.assertTrue(isinstance(v, ValueForFromDictTest))
     self.assertEquals(v.units, 'unit')
+    self.assertTrue(v.higher_is_better)
 
   def testFromDictWithPage(self):
     page0 = self.pages[0]