[Telemetry] Add 'check_independent' command to benchmark_runner

telemetry/telemetry/benchmark_runner.py

Index: telemetry/telemetry/benchmark_runner.py
diff --git a/telemetry/telemetry/benchmark_runner.py b/telemetry/telemetry/benchmark_runner.py
index 598bc5315e1937707c3cb2461f00a39586ab008f..1212a0e2f9196f0686abfbea8fce81c413a58c54 100644
--- a/telemetry/telemetry/benchmark_runner.py
+++ b/telemetry/telemetry/benchmark_runner.py
@@ -196,7 +196,7 @@ class Run(command_line.OptparseCommand):
       matching_benchmark.SetArgumentDefaults(parser)
 
   @classmethod
-  def ProcessCommandLineArgs(cls, parser, args, environment):
+  def _FindBenchmark(cls, parser, args, environment):
     all_benchmarks = _Benchmarks(environment)
     if not args.positional_args:
       possible_browser = (
@@ -231,6 +231,12 @@ class Run(command_line.OptparseCommand):
     assert issubclass(benchmark_class, benchmark.Benchmark), (
         'Trying to run a non-Benchmark?!')
 
+    return benchmark_class
+
+  @classmethod
+  def ProcessCommandLineArgs(cls, parser, args, environment):
+    benchmark_class = cls._FindBenchmark(parser, args, environment)
+
     benchmark.ProcessCommandLineArgs(parser, args)
     benchmark_class.ProcessCommandLineArgs(parser, args)
 
@@ -240,6 +246,22 @@ class Run(command_line.OptparseCommand):
     return min(255, self._benchmark().Run(args))
 
 
+class CheckIndependent(Run):
+  """Return 0 if benchmark stories are independent, 1 if not."""
+
+  usage = '[benchmark_name]'
+
+  @classmethod
+  def ProcessCommandLineArgs(cls, parser, args, environment):
+    cls._benchmark = cls._FindBenchmark(parser, args, environment)
+
+  def Run(self, args):
+    if self._benchmark.ShouldTearDownStateAfterEachStoryRun():
+      sys.exit(0)
+    else:
+      sys.exit(1)
+
+
 def _ScriptName():
   return os.path.basename(sys.argv[0])
 
@@ -401,7 +423,7 @@ def main(environment, extra_commands=None, **log_config_kwargs):
 
   if extra_commands is None:
     extra_commands = []
-  all_commands = [Help, List, Run] + extra_commands
+  all_commands = [Help, CheckIndependent, List, Run] + extra_commands
 
   # Validate and interpret the command name.
   commands = _MatchingCommands(command_name, all_commands)
@@ -417,7 +439,8 @@ def main(environment, extra_commands=None, **log_config_kwargs):
   else:
     command = Run
 
-  binary_manager.InitDependencyManager(environment.client_configs)
+  if binary_manager.NeedsInit():
+    binary_manager.InitDependencyManager(environment.client_configs)
 
   # Parse and run the command.
   parser = command.CreateParser()