Update reference to page_test module to use legacy_page_test module

content/test/gpu/gpu_tests/trace_test.py

Index: content/test/gpu/gpu_tests/trace_test.py
diff --git a/content/test/gpu/gpu_tests/trace_test.py b/content/test/gpu/gpu_tests/trace_test.py
index fc30ebb4c03677f6c23988d37217fec482a87f9a..996cccac245dcf8c4457fdbae4ab9a6f86adbc84 100644
--- a/content/test/gpu/gpu_tests/trace_test.py
+++ b/content/test/gpu/gpu_tests/trace_test.py
@@ -5,7 +5,7 @@ from gpu_tests import gpu_test_base
 from gpu_tests import trace_test_expectations
 import page_sets
 
-from telemetry.page import page_test
+from telemetry.page import legacy_page_test
 from telemetry.timeline import model as model_module
 from telemetry.timeline import tracing_config
 
@@ -60,7 +60,7 @@ class TraceValidatorBase(gpu_test_base.ValidatorBase):
           event.category == category_name):
         break
     else:
-      raise page_test.Failure(self._FormatException(category_name))
+      raise legacy_page_test.Failure(self._FormatException(category_name))
 
   def CustomizeBrowserOptions(self, options):
     options.AppendExtraBrowserArgs('--enable-logging')