Sync to latest trace-viewer

bug:20761637

Cherry-pick of 26c92f4cb78a275f1ebb94dd976f37bdd7d53ce7 from AOSP

Change-Id: I645b485ff2643b6efbec1fa25de6fc81a98c3ee5
diff --git a/trace-viewer/PRESUBMIT.py b/trace-viewer/PRESUBMIT.py
index 0d2b415..a40b08d 100644
--- a/trace-viewer/PRESUBMIT.py
+++ b/trace-viewer/PRESUBMIT.py
@@ -1,8 +1,24 @@
 # Copyright 2015 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 sys
+
+
+def CheckChange(input_api, output_api):
+  original_sys_path = sys.path
+  try:
+    sys.path += [input_api.PresubmitLocalPath()]
+    from hooks import pre_commit
+    results = pre_commit.GetResults('@{u}')
+    return map(output_api.PresubmitError, results)
+  finally:
+    sys.path = original_sys_path
+
+
 def CheckChangeOnUpload(input_api, output_api):
-  return []
+  return CheckChange(input_api, output_api)
+
 
 def CheckChangeOnCommit(input_api, output_api):
-  return []
+  return CheckChange(input_api, output_api)