Telemetry / Memory benchmark fix: Separate histograms for different tests.

tools/telemetry/telemetry/util_unittest.py

Index: tools/telemetry/telemetry/util_unittest.py
diff --git a/tools/telemetry/telemetry/util_unittest.py b/tools/telemetry/telemetry/util_unittest.py
index 5d144e38059ac325913fe1931b92812ceb2c23ca..3704470b21cdd76d562f2d5a077ba5c06f688438 100644
--- a/tools/telemetry/telemetry/util_unittest.py
+++ b/tools/telemetry/telemetry/util_unittest.py
@@ -1,6 +1,7 @@
 # Copyright (c) 2012 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.
+import json
 import unittest
 
 from telemetry import util
@@ -16,3 +17,22 @@ class TestWait(unittest.TestCase):
     def test():
       return False
     self.assertRaises(util.TimeoutException, lambda: util.WaitFor(test, 0.1))
+
+  def testSubtractHistogram(self):
+    baseline_histogram = """{"count": 3, "buckets": [
+{"low": 1, "high": 2, "count": 1},
+{"low": 2, "high": 3, "count": 2}]}"""
+
+    histogram = """{"count": 14, "buckets": [
+{"low": 1, "high": 2, "count": 1},
+{"low": 2, "high": 3, "count": 3},
+{"low": 3, "high": 4, "count": 10}]}"""
+
+    new_histogram = json.loads(
+        util.SubtractHistogram(histogram, baseline_histogram))
+    new_buckets = dict()
+    for b in new_histogram['buckets']:
+      new_buckets[b['low']] = b['count']
+    self.assertFalse(1 in new_buckets)
+    self.assertEquals(1, new_buckets[2])
+    self.assertEquals(10, new_buckets[3])