1 files changed, 11 insertions, 12 deletions
diff --git a/chromium/third_party/catapult/tracing/tracing_build/merge_traces.py b/chromium/third_party/catapult/tracing/tracing_build/merge_traces.py
index df1029a8805..5294a7ea412 100644
--- a/chromium/third_party/catapult/tracing/tracing_build/merge_traces.py
+++ b/chromium/third_party/catapult/tracing/tracing_build/merge_traces.py
@@ -10,6 +10,7 @@ import argparse
 import codecs
 import collections
 import gzip
+import io
 import itertools
 import json
 import logging
@@ -93,11 +94,12 @@ class IdMap(object):
     assert 'id' not in items  # ID is set according to the path.
     for key, value in items.items():
       value_set = self._items[key]
-      if (isinstance(value, collections.Iterable) and
+      if (isinstance(value, collections.abc.Iterable) and
           not isinstance(value, StringTypes)):
         value_set.update(value)
       else:
         value_set.add(value)
+    return None
 
   def MapEntry(self, source, path):
     """Map an source-specific entry ID path to a canonical entry ID path.
@@ -288,9 +290,8 @@ class IdMap(object):
     cls_name = type(self).__name__
     if self._depth == 0:
       return '%s root' % cls_name
-    else:
-      return '%s %s entry(%s)' % (cls_name, self.LEVELS[self._depth - 1].name,
-                                  self._items)
+    return '%s %s entry(%s)' % (cls_name, self.LEVELS[self._depth - 1].name,
+                                self._items)
 
 
 class ProcessIdMap(IdMap):
@@ -310,19 +311,18 @@ def LoadTrace(filename):
   logging.info('Loading trace %r...', filename)
   if filename.endswith(HTML_FILENAME_SUFFIX):
     return LoadHTMLTrace(filename)
-  elif filename.endswith(GZIP_FILENAME_SUFFIX):
+  if filename.endswith(GZIP_FILENAME_SUFFIX):
     with gzip.open(filename, 'rb') as f:
       return json.load(f)
-  else:
-    with open(filename, 'r') as f:
-      return json.load(f)
+  with open(filename, 'r') as f:
+    return json.load(f)
 
 
 def LoadHTMLTrace(filename):
   """Load a trace from a vulcanized HTML trace file."""
   trace_components = collections.defaultdict(list)
 
-  with open(filename) as file_handle:
+  with io.open(filename, 'r', encoding='utf-8') as file_handle:
     for sub_trace in html2trace.ReadTracesFromHTMLFile(file_handle):
       for name, component in TraceAsDict(sub_trace).items():
         trace_components[name].append(component)
@@ -406,8 +406,7 @@ def MergeComponents(component_name, components_by_filename):
   """Merge a component of multiple JSON traces into a single component."""
   if component_name == 'traceEvents':
     return MergeTraceEvents(components_by_filename)
-  else:
-    return MergeGenericTraceComponents(component_name, components_by_filename)
+  return MergeGenericTraceComponents(component_name, components_by_filename)
 
 
 def MergeTraceEvents(events_by_filename):
@@ -645,7 +644,7 @@ def MergeGenericTraceComponents(component_name, components_by_filename):
   provided value (in some trace).
   """
   components = list(components_by_filename.values())
-  first_component = next(components)
+  first_component = next(iter(components))
   if not all(c == first_component for c in components):
     logging.warning(
         'Values of trace component %r differ across the provided traces. '