[Perf Waterfall] Remove option to create a shard map for a single benchmark.

This feature was originally intended for Pinpoint's use,
but that never happened. Supporting this feature would complicate
my work in crbug.com/965158. We can re-add this feature
later if Pinpoint ever wants it.

Bug: 965158
Change-Id: Ifef1e2ae844b5bd047e033461a4f9a0bb116c5af
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1935748Reviewed-by: John Chen <johnchen@chromium.org>
Commit-Queue: Caleb Rouleau <crouleau@chromium.org>
Cr-Commit-Position: refs/heads/master@{#719239}

tools/perf/generate_perf_sharding

@@ -70,26 +70,6 @@ def GetParser():
   _AddBuilderPlatformSelectionArgs(parser_update_timing)
   parser_update_timing.set_defaults(func=_UpdateTimingDataCommand)
 
-  parser_create = subparsers.add_parser(
-      'create',
-      help='Create a shard map for a single benchmark.')
-  parser_create.add_argument(
-      '--benchmark', help='The benchmark that you want to create shard for',
-      required=True)
-  parser_create.add_argument(
-      '--timing-data-source', '-t', choices=bot_platforms.ALL_PLATFORM_NAMES,
-      help='The timing data that you want to use. If not set, it will assume '
-           'all stories use the same amount of time to run')
-  parser_create.add_argument(
-      # pinpoint typically has 16 machines for each hardware types, so we set
-      # the default to use half of them to avoid starving the pool.
-      '--shards-num', type=int, default=8,
-      help="The number of shards you'd like to use, default is %(default)s")
-  parser_create.add_argument(
-      '--output-path', default='new_shard_map.json',
-      help='Output file path for the shard map, default is `%(default)s`')
-  parser_create.set_defaults(func=_CreateShardMapForBenchmark)
-
   parser_deschedule = subparsers.add_parser(
       'deschedule',
       help=('After you deschedule one or more '
@@ -165,14 +145,13 @@ def _LoadTimingData(args):
 
 
 def _GenerateShardMap(
-    builder, num_of_shards, output_path, debug, benchmark):
+    builder, num_of_shards, output_path, debug):
   timing_data = []
   if builder:
     with open(builder.timing_file_path) as f:
       timing_data = json.load(f)
   benchmarks_to_shard = _GenerateBenchmarksToShardsList(
-      [b for b in builder.benchmarks_to_run if not benchmark or (
-          b.Name() == benchmark)])
+      list(builder.benchmarks_to_run))
   sharding_map = sharding_map_generator.generate_sharding_map(
       benchmarks_to_shard, timing_data, num_shards=num_of_shards,
       debug=debug)
@@ -236,30 +215,10 @@ def _UpdateShardsForBuilders(args):
     _UpdateTimingData(builders)
   for b in builders:
     _GenerateShardMap(
-        b, b.num_shards, b.shards_map_file_path, args.debug, benchmark=None)
+        b, b.num_shards, b.shards_map_file_path, args.debug)
     print('Updated sharding map for %s' % repr(b.name))
 
 
-def _CreateShardMapForBenchmark(args):
-  """Create the shard map for the given benchmark.
-
-  Args:
-    args(Namespace object): the namespace object for the subparser `create`. It
-      will contain the attributes:
-        `benchmark`: the name of the benchmark that we want the shard for
-        `num_shards`: the total number of shards that we want to use
-        `output_path`: the output file path for the shard map
-        `builder`: the builder name, unlike the above, this is a string instead
-          of a list of string like above
-  """
-  builder = None
-  if args.timing_data_source:
-    [builder] = [b for b in bot_platforms.ALL_PLATFORMS
-                 if b.name == args.timing_data_source]
-  _GenerateShardMap(
-      builder, args.shards_num, args.output_path, args.debug, args.benchmark)
-
-
 def _DescheduleBenchmark(args):
   """Remove benchmarks from the shard maps without re-sharding."""
   del args