Add LayoutTest for PerformanceObserver inside Worker

third_party/WebKit/LayoutTests/TestExpectations

Index: third_party/WebKit/LayoutTests/TestExpectations
diff --git a/third_party/WebKit/LayoutTests/TestExpectations b/third_party/WebKit/LayoutTests/TestExpectations
index fef8a6114ccb8c2a19698438cdcb333ed5624c34..75861e7bc9673ad8dcbab58d80910f0db8ac5d16 100644
--- a/third_party/WebKit/LayoutTests/TestExpectations
+++ b/third_party/WebKit/LayoutTests/TestExpectations
@@ -2876,6 +2876,7 @@ crbug.com/727505 [ Linux Mac Win ] virtual/threaded/fast/compositorworker/reques
 crbug.com/727991 [ Linux Mac Win ] virtual/threaded/fast/compositorworker/visual-update.html [ Pass Failure Timeout Crash ]
 
 crbug.com/729836 [ Win ] fast/workers/worker-document-leak.html [ Pass Failure ]
+crbug.com/705820 fast/workers/worker-with-performance-observer.html [ Failure ]

[falken, 2017/07/04 14:46:35]

Why add a test that's failing? Instead of a Failure line here, it should have a
-expected.txt file instead.

[npm, 2017/07/05 21:53:53]

Because this is actually not working. We will enable once the bug referenced is
fixed.

[falken, 2017/07/05 23:30:08]

I can't find where this is documented now, but it's recommended practice to use
an -expected.txt file instead of [ Failure ] even if the expected test output is
not ultimately what's "correct". It allows us to catch unexpected regressions in
test output. I.e., we basically should never have [ Failure ] lines unless the
test is flakily failing in different ways.

 
 # Sensor tests fail on Mac swarming
 crbug.com/731018 [ Mac ] sensor/accelerometer.html [ Failure Pass Crash ]