gpu tests: Update the screenshot test.

Bump the repetition back to 20, but increase the timeout for taking the
screenshots from 5 seconds to 10 seconds instead.

BUG=853762

Cq-Include-Trybots: luci.chromium.try:android_optional_gpu_tests_rel;luci.chromium.try:linux_optional_gpu_tests_rel;luci.chromium.try:mac_optional_gpu_tests_rel;luci.chromium.try:win_optional_gpu_tests_rel
Change-Id: Id6914cf7c1791f654d35725644bad7d8fec22073
Reviewed-on: https://chromium-review.googlesource.com/1107201
Commit-Queue: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Kenneth Russell <kbr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#569535}

content/test/gpu/gpu_tests/screenshot_sync_integration_test.py

@@ -118,7 +118,7 @@ class ScreenshotSyncIntegrationTest(gpu_integration_test.GpuIntegrationTest):
     tab.EvaluateJavaScript(
         "window.draw({{ red }}, {{ green }}, {{ blue }});",
         red=canvasRGB.r, green=canvasRGB.g, blue=canvasRGB.b)
-    screenshot = tab.Screenshot(5)
+    screenshot = tab.Screenshot(10)
     start_x = 10
     start_y = 0
     outer_size = 256
@@ -131,7 +131,7 @@ class ScreenshotSyncIntegrationTest(gpu_integration_test.GpuIntegrationTest):
     browser_arg = args[0]
     self.RestartBrowserIfNecessaryWithArgs(self._AddDefaultArgs([browser_arg]))
     self._Navigate(test_path)
-    repetitions = 10
+    repetitions = 20
     for _ in range(0, repetitions):
       self._CheckScreenshot()