Wait for 60 frames before DirectComposition_ComplexOverlays test.

We still saw flakinees in VideoPathTraceTest_DirectComposition_ComplexOverlays.
Increase the wait time to 60 swapped frames before checking the result. We
have to make sure the video frame is ready.

Bug: 937545
Change-Id: I1a4d2b84a90a359c93b7f4695a4c3610f6528c88
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1500787Reviewed-by: Antoine Labour <piman@chromium.org>
Reviewed-by: Zhenyao Mo <zmo@chromium.org>
Commit-Queue: Maggie Chen <magchen@chromium.org>
Cr-Commit-Position: refs/heads/master@{#637551}

content/test/data/gpu/pixel_video_test.js

@@ -5,8 +5,8 @@
 var video;
 
 // Some videos are less than 60 fps, so actual video frame presentations
-// could be much less than 30.
-var g_swaps_before_success = 30
+// could be much less than 60.
+var g_swaps_before_success = 60
 
 function main() {
   video = document.getElementById("video");

content/test/gpu/gpu_tests/trace_test_expectations.py

@@ -31,6 +31,3 @@ class TraceTestExpectations(GpuTestExpectations):
     self.Fail('VideoPathTraceTest_DirectComposition_Video_VP9_Fullsize',
         ['win', 'intel'], bug=930343)
 
-    # Flaky on Win10.
-    self.Flaky('VideoPathTraceTest_DirectComposition_ComplexOverlays',
-        ['win10'], bug=937545)