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

tools/telemetry/telemetry/value/summary.py

Index: tools/telemetry/telemetry/value/summary.py
diff --git a/tools/telemetry/telemetry/value/summary.py b/tools/telemetry/telemetry/value/summary.py
index 13e8ac20dfc52ba5b387fa9940d4d82099cbc6f5..59e9ad24d07bf376ccc9b6efd82c55f81a01bb1d 100644
--- a/tools/telemetry/telemetry/value/summary.py
+++ b/tools/telemetry/telemetry/value/summary.py
@@ -7,6 +7,7 @@ from collections import defaultdict
 from telemetry.value import failure
 from telemetry.value import merge_values
 from telemetry.value import skip
+from telemetry.value import summarizable
 
 
 class Summary(object):
@@ -67,6 +68,10 @@ class Summary(object):
         v for v in all_page_specific_values if not (isinstance(
             v, failure.FailureValue) or isinstance(v, skip.SkipValue))]
 
+    # All successful values must be summarizable.
+    for v in all_successful_page_values:
+      assert isinstance(v, summarizable.SummarizableValue), "Not summarizable: %r" % v

[qyearsley, 2015/01/27 00:50:46]

Looks like it's just over 80 chars. Also, I think single quotes are preferred
over double, quotes, so, this could be formatted as:

assert isinstance(v, summarizable.SummarizableValue), ('Not summariz'
                                                       'able: %r' % v)

or

is_summarizable = isinstance(v, summarizable.SummarizableValue)
assert is_summarizable, 'Not summarizable: %r' % v

or, maybe it's appropriate use a different kind of exception here?

+
     # We will later need to determine how many values were originally created
     # for each value name, to apply a workaround meant to clean up the printf
     # output.