Add FailureValue and wire it through PageTestResults.

tools/telemetry/telemetry/value/merge_values.py

Index: tools/telemetry/telemetry/value/merge_values.py
diff --git a/tools/telemetry/telemetry/value/merge_values.py b/tools/telemetry/telemetry/value/merge_values.py
index 30c999db8648d4f9b7f10366df7e31935be407d4..89d187824e19fd7e5bb7a45083cae1f6e45f3e0d 100644
--- a/tools/telemetry/telemetry/value/merge_values.py
+++ b/tools/telemetry/telemetry/value/merge_values.py
@@ -1,6 +1,9 @@
 # Copyright 2013 The Chromium Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
+
+from telemetry.value import failure
+
 def MergeLikeValuesFromSamePage(all_values):
   """Merges values that measure the same thing on the same page.
 
@@ -108,6 +111,12 @@ def GroupStably(all_values, key_func):
   merge_groups = {}
   merge_groups_in_creation_order = []
   for value in all_values:
+    # TODO(chrishenry): This is temporary. When we figure out the
+    # right summarization strategy for page runs with failures, we
+    # should use that instead.
+    if isinstance(value, failure.FailureValue):
+      continue
+
     key = key_func(value)
     if key not in merge_groups:
       merge_groups[key] = []