[Perf] Update references to telemetry.core.discover

chrome/test/media_router/telemetry/benchmarks/pagesets/__init__.py

Index: chrome/test/media_router/telemetry/benchmarks/pagesets/__init__.py
diff --git a/chrome/test/media_router/telemetry/benchmarks/pagesets/__init__.py b/chrome/test/media_router/telemetry/benchmarks/pagesets/__init__.py
index 3eea54149f664e5c3c9fd6a6549b9389853324d1..199715520a214c9e558709467af2410a067eb04b 100644
--- a/chrome/test/media_router/telemetry/benchmarks/pagesets/__init__.py
+++ b/chrome/test/media_router/telemetry/benchmarks/pagesets/__init__.py
@@ -6,9 +6,9 @@ import inspect
 import os
 import sys
 
-from telemetry.core import discover
 from telemetry import story
 
+from py_utils import discover
 
 # Import all submodules' StorySet classes.
 start_dir = os.path.dirname(os.path.abspath(__file__))
@@ -16,4 +16,4 @@ top_level_dir = os.path.abspath(os.path.join(start_dir, os.pardir, os.pardir))
 base_class = story.StorySet
 for cls in discover.DiscoverClasses(
     start_dir, top_level_dir, base_class).values():
-  setattr(sys.modules[__name__], cls.__name__, cls)
+  setattr(sys.modules[__name__], cls.__name__, cls)