graphics_per-day suite: Increase timeout to 6h.

Some graphics_dEQP*master tests can take more than 4h on slow boards.

TEST=None.
BUG=chrome-os-partner:54126

Change-Id: I0564414a1fa15280d35cc16ebde06ee8f1e929f8
Reviewed-on: https://chromium-review.googlesource.com/352880
Trybot-Ready: Ilja H. Friedel <ihf@chromium.org>
Tested-by: Ilja H. Friedel <ihf@chromium.org>
Reviewed-by: Dan Shi <dshi@google.com>
Reviewed-by: Daniel Kurtz <djkurtz@chromium.org>
diff --git a/test_suites/control.graphics_per-day b/test_suites/control.graphics_per-day
index fbb3f14..dd49671 100644
--- a/test_suites/control.graphics_per-day
+++ b/test_suites/control.graphics_per-day
@@ -29,7 +29,7 @@
 from autotest_lib.server.cros import provision
 from autotest_lib.server.cros.dynamic_suite import dynamic_suite
 
-args_dict['max_runtime_mins'] = 240
+args_dict['max_runtime_mins'] = 360
 args_dict['add_experimental'] = True
 args_dict['name'] = 'graphics_per-day'
 args_dict['version_prefix'] = provision.CROS_VERSION_PREFIX