Skip the screenshot_sync test properly.

content/test/gpu/gpu_tests/screenshot_sync.py

Index: content/test/gpu/gpu_tests/screenshot_sync.py
diff --git a/content/test/gpu/gpu_tests/screenshot_sync.py b/content/test/gpu/gpu_tests/screenshot_sync.py
index c62865cbc80bb31db1e94dcbc5d351864af4256c..caa38532119b10674f379ee5ac87956996343374 100644
--- a/content/test/gpu/gpu_tests/screenshot_sync.py
+++ b/content/test/gpu/gpu_tests/screenshot_sync.py
@@ -8,7 +8,6 @@ from gpu_tests import gpu_test_base
 from gpu_tests import path_util
 from gpu_tests import screenshot_sync_expectations
 
-from telemetry import benchmark
 from telemetry.page import page_test
 from telemetry.story import story_set as story_set_module
 from telemetry.util import image_util
@@ -55,7 +54,6 @@ class ScreenshotSyncPage(gpu_test_base.PageBase):
       expectations=expectations)
 
 
-@benchmark.Disabled('linux', 'mac', 'win')
 class ScreenshotSyncProcess(gpu_test_base.TestBase):
   """Tests that screenhots are properly synchronized with the frame one which
   they were requested"""