[ElementTiming] Fix flaky observe-child-element.html

The timeout used to bail out early is causing flakiness, so this change
removes that timeout since it is not needed for the test. It also
increases the timeout used in cross-origin-iframe-element.html to give
chance for the entry to be dispatched. Since this test passes when such
entry is NOT dispatched, that test is not currently flaky.

Bug: 879270, 896765
Change-Id: Ie02a9787d721e6c0d1f347b0d08dd9dbd985ca79
Reviewed-on: https://chromium-review.googlesource.com/c/1363960Reviewed-by: Timothy Dresser <tdresser@chromium.org>
Commit-Queue: Nicolás Peña Moreno <npm@chromium.org>
Cr-Commit-Position: refs/heads/master@{#614753}

third_party/blink/web_tests/TestExpectations

@@ -5620,11 +5620,6 @@ crbug.com/891155 [ Linux ] fast/events/middleClickAutoscroll-drag.html [ Failure
 crbug.com/895777 external/wpt/css/css-transforms/text-perspective-001.html [ Pass Crash ]
 crbug.com/895777 external/wpt/infrastructure/assumptions/blank.html [ Failure Crash ]
 
-#Sheriff 2018-10-18
-crbug.com/896765 [ Linux ] http/tests/performance-timing/element-timing/observe-child-element.html [ Failure Pass ]
-crbug.com/896765 [ Mac ] http/tests/performance-timing/element-timing/observe-child-element.html [ Failure Pass ]
-crbug.com/896765 [ Win ] http/tests/performance-timing/element-timing/observe-child-element.html [ Failure Pass ]
-
 #Sheriff 2018-10-23
 crbug.com/898214 [ Mac10.11 ] virtual/outofblink-cors-ns/external/wpt/fetch/api/credentials/authentication-basic.any.html [ Failure ]
 crbug.com/898050 [ Mac ] fast/workers/taskqueue/basic.html [ Pass Timeout ]

third_party/blink/web_tests/http/tests/performance-timing/element-timing/cross-origin-iframe-element.html

@@ -26,7 +26,7 @@
     t.step_timeout( () => {
       // After some wait, assume observer did not receive the entry, so the test passes.
       t.done();
-    }, 100);
+    }, 300);
   }, 'Element from cross origin iframe is NOT observable.');
 </script>
 

third_party/blink/web_tests/http/tests/performance-timing/element-timing/observe-child-element.html

@@ -33,10 +33,6 @@ body {
       document.body.appendChild(iframe);
       beforeRender = performance.now();
     };
-    t.step_timeout( () => {
-      // We were idle long enough to wait for PerfomanceObserver callback.
-      assert_unreached("PerformanceObserver callback should have been fired.");
-    }, 100);
   }, 'Element from same-origin iframe is observable.');
 </script>