The integrationDriver function has a responseDataCallback 
which you can customize. 
By default, it writes the results to the integration_response_data.json file,
but you can customize it to generate a summary like in this example.

4. Run the test

After configuring the test to capture a performance Timeline and save a
summary of the results to disk, run the test with the following command:

The --profile option means to compile the app for the “profile mode” 
rather than the “debug mode”, so that the benchmark result is closer to 
what will be experienced by end users.

Note:
  Run the command with --no-dds when running on a mobile device or emulator.
  This option disables the Dart Development Service (DDS), which won’t
  be accessible from your computer.

5. Review the results

After the test completes successfully, the build directory at the root of
the project contains two files: