[telemetry] Add Html2OutputFormatter for generating results2.html

telemetry/telemetry/internal/results/page_test_results.py

Index: telemetry/telemetry/internal/results/page_test_results.py
diff --git a/telemetry/telemetry/internal/results/page_test_results.py b/telemetry/telemetry/internal/results/page_test_results.py
index 95a607fc50dcae45a745c5fcdd883dca6bd6da1b..aee0d95fc6ebb23d0d49d01b4649bc765f5343f6 100644
--- a/telemetry/telemetry/internal/results/page_test_results.py
+++ b/telemetry/telemetry/internal/results/page_test_results.py
@@ -63,6 +63,15 @@ class PageTestResults(object):
     self._pages_to_profiling_files = collections.defaultdict(list)
     self._pages_to_profiling_files_cloud_url = collections.defaultdict(list)
 
+    # You'd expect this to be a set(), but Values are dictionaries, which are
+    # unhashable. We could wrap Values with custom __eq/hash__, but we don't
+    # actually need set-ness in python.
+    self._value_set = []
+
+  @property
+  def value_set(self):
+    return self._value_set
+
   def __copy__(self):
     cls = self.__class__
     result = cls.__new__(cls)