[Telemetry] Explicitly define Name() method for all perf benchmarks

tools/perf/benchmarks/v8.py

 # Copyright 2014 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 page_sets
 from telemetry.web_perf import timeline_based_measurement
 from telemetry import benchmark
 
 
 @benchmark.Disabled('win')  # crbug.com/416502
 class V8GarbageCollectionCases(benchmark.Benchmark):
   """Measure V8 metrics on the garbage collection cases."""
   def CreateTimelineBasedMeasurementOptions(self):
     # TODO(ernstm): Remove v8-overhead when benchmark relevant v8 events become
     # available in the 'benchmark' category.
     return timeline_based_measurement.Options(overhead_level='v8-overhead')
 
+  @classmethod
+  def Name(cls):
+    return 'v8.garbage_collection_cases'
+
   page_set = page_sets.GarbageCollectionCasesPageSet