A custom AndroidBenchmarkRunner for benchmarks on CI

BenchmarkRunner.kt

  class BenchmarkRunner : AndroidBenchmarkRunner() {

    override fun newApplication(
      cl: ClassLoader?,
      className: String?,
      context: Context?
    ): Application {
      // Create an instance of our custom Application class for benchmark tests 
      return super.newApplication(cl, BenchmarkApp::class.java.name, context)
    }

    override fun onCreate(arguments: Bundle?) {
      val newArguments = arguments ?: Bundle()

      /* This is how we enable output on FirebaseTestLab, as the
         environment variable name isn't valid there. */
      newArguments.putString("androidx.benchmark.output.enable", "true")
      
      super.onCreate(newArguments)
    }
  }