Add a tool that strips all but the first memory dump from a trace.

tools/memory_inspector/strip_memory_dumps_from_trace.py

Index: tools/memory_inspector/strip_memory_dumps_from_trace.py
diff --git a/tools/memory_inspector/strip_memory_dumps_from_trace.py b/tools/memory_inspector/strip_memory_dumps_from_trace.py
new file mode 100755
index 0000000000000000000000000000000000000000..8f7ecf174e8822a4f32998ec2a92a986a836e49c
--- /dev/null
+++ b/tools/memory_inspector/strip_memory_dumps_from_trace.py
@@ -0,0 +1,63 @@
+#!/usr/bin/env python
+# Copyright 2017 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.
+
+"""
+Removes all memory dump trace events that are not associated with the first,
+detailed dump.
+"""
+
+import argparse
+import json
+import sys
+
+
+def main():
+  parser = argparse.ArgumentParser()
+  parser.add_argument('input_file',
+                      help = 'The file to process. Should be in json.')
+  parser.add_argument('output_file',
+                      help = 'The file to emit. Will be in json.')
+  parser_args = parser.parse_args()
+
+  f = open(parser_args.input_file, 'r')
+  contents = f.read()
+  json_contents = json.loads(contents)
+
+  def IsMemoryDumpEvent(event):
+    return event['ph'] == 'v'
+
+  def IsDetailed(event):
+    if not IsMemoryDumpEvent(event):
+      return False
+    level = event['args']['dumps']['level_of_detail']
+    return level == "detailed"
+
+  def IsLight(event):
+    if not IsMemoryDumpEvent(event):
+      return False
+    level = event['args']['dumps']['level_of_detail']
+    return level != "detailed"
+
+  # Find the id associated with the first detailed memory dump.
+  identifier = None
+  for event in json_contents['traceEvents']:
+    if IsDetailed(event):
+      identifier = event['id']
+      break
+
+  trace_events = []
+  for event in json_contents['traceEvents']:
+    if IsDetailed(event) and event['id'] != identifier:
+      continue
+    if IsLight(event):
+      continue
+    trace_events.append(event)
+
+  json_contents['traceEvents'] = trace_events
+  f2 = open(parser_args.output_file, 'w')
+  f2.write(json.dumps(json_contents))
+
+if __name__ == '__main__':
+  sys.exit(main())