[telemetry] Prototype for specifying page sets using Python imports and Telemetry discovery.

tools/telemetry/telemetry/page/record_wpr.py

Index: tools/telemetry/telemetry/page/record_wpr.py
diff --git a/tools/telemetry/telemetry/page/record_wpr.py b/tools/telemetry/telemetry/page/record_wpr.py
index c8ba504c0af9dd6aebaa9cda4e022c0799043614..b1c03d5ec941fe670880bc54c05250490718688b 100755
--- a/tools/telemetry/telemetry/page/record_wpr.py
+++ b/tools/telemetry/telemetry/page/record_wpr.py
@@ -89,10 +89,14 @@ def Main(base_dir):
       if not issubclass(cls, profile_creator.ProfileCreator)
       }
   tests = discover.DiscoverClasses(base_dir, base_dir, test.Test,
-                                   index_by_class_name=True)
+                                   index_by_class_name=True).values()
+  tests = {test_class.Name(): test_class for test_class in tests}
+  page_sets = discover.DiscoverClasses(base_dir, base_dir, page_set.PageSet,
+                                       index_by_class_name=True).values()
+  page_sets = {ps.Name(): ps for ps in page_sets}
 
   options = browser_options.BrowserFinderOptions()
-  parser = options.CreateParser('%prog <PageSet|Test|URL>')
+  parser = options.CreateParser('%prog <PageSet|Test>')
   page_runner.AddCommandLineArgs(parser)
 
   recorder = RecordPage(measurements)
@@ -110,9 +114,9 @@ def Main(base_dir):
     parser.parse_args()
     recorder.test.ProcessCommandLineArgs(parser, options)
     ps = tests[target]().CreatePageSet(options)
-  elif discover.IsPageSetFile(target):
+  elif target in page_sets:
     parser.parse_args()
-    ps = page_set.PageSet.FromFile(target)
+    ps = tests[target]()
   else:
     parser.print_usage()
     sys.exit(1)