[Telemetry] Add Expectation module that enables disabling benchmarks/stories

telemetry/telemetry/benchmark.py

Index: telemetry/telemetry/benchmark.py
diff --git a/telemetry/telemetry/benchmark.py b/telemetry/telemetry/benchmark.py
index 3cf78fff127ea76d48d82ad35835ba8c632fda79..a8fd2f12225e84c2161e5302333e03fc9864da49 100644
--- a/telemetry/telemetry/benchmark.py
+++ b/telemetry/telemetry/benchmark.py
@@ -8,6 +8,7 @@ from telemetry import decorators
 from telemetry.internal import story_runner
 from telemetry.internal.util import command_line
 from telemetry.page import legacy_page_test
+from telemetry.story import expectations
 from telemetry.web_perf import timeline_based_measurement
 
 Disabled = decorators.Disabled
@@ -265,6 +266,14 @@ class Benchmark(command_line.Command):
       raise NotImplementedError('This test has no "page_set" attribute.')
     return self.page_set()  # pylint: disable=not-callable
 
+  def GetExpectations(self):
+    """Returns a StoryExpectation object.
+
+    This object is used to determine what stories are disabled. This needs to be
+    overridden by the subclass. It defaults to an empty expectations object.
+    """
+    return expectations.StoryExpectations()
+
 
 def AddCommandLineArgs(parser):
   story_runner.AddCommandLineArgs(parser)