telemetry: fix start_with_url benchmark.

tools/perf/benchmarks/start_with_url.py

Index: tools/perf/benchmarks/start_with_url.py
diff --git a/tools/perf/benchmarks/start_with_url.py b/tools/perf/benchmarks/start_with_url.py
index f9c199b6a4f80f7693929a2f746de1aaff1df206..895dd9116c37f4ee3bea907fe4a9820ca628cd8c 100644
--- a/tools/perf/benchmarks/start_with_url.py
+++ b/tools/perf/benchmarks/start_with_url.py
@@ -7,21 +7,26 @@ import page_sets
 from telemetry import benchmark
 
 
+class _StartWithUrl(benchmark.Benchmark):
+  page_set = page_sets.StartupPagesPageSet
+  test = startup.StartWithUrl
+
+  def CreatePageTest(self, options):
+    is_cold = (self.tag == 'cold')
+    return self.test(cold=is_cold)
+
+
 @benchmark.Enabled('has tabs')
 @benchmark.Disabled('chromeos', 'linux', 'mac', 'win')
-class StartWithUrlCold(benchmark.Benchmark):
+class StartWithUrlCold(_StartWithUrl):
   """Measure time to start Chrome cold with startup URLs"""
   tag = 'cold'
-  test = startup.StartWithUrl(cold=True)
-  page_set = page_sets.StartupPagesPageSet
   options = {'pageset_repeat': 5}
 
 
 @benchmark.Enabled('has tabs')
 @benchmark.Disabled('chromeos', 'linux', 'mac', 'win')
-class StartWithUrlWarm(benchmark.Benchmark):
+class StartWithUrlWarm(_StartWithUrl):
   """Measure time to start Chrome warm with startup URLs"""
   tag = 'warm'
-  test = startup.StartWithUrl(cold=False)
-  page_set = page_sets.StartupPagesPageSet
   options = {'pageset_repeat': 10}