Fix test expectations for throttling tests

A couple of flaky render throttling tests appear to have been un-flaked,
probably by recent changes to the render throttling code, in particular
this one:

https://chromium-review.googlesource.com/c/chromium/src/+/1600078

timer-throttling-hidden-page.html turned flaky in 2015 and was disabled in
2017. In 2018, the test was changed to remove references to
visibility=prerender, but the expectations were never updated (presumably
because the test was disabled).

BUG=956547,520170,956354
R=chrishtr@chromium.org

Change-Id: Id49f0449a091b3ba548f64bc43576a16bce83e35
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1642031Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: Stefan Zager <szager@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665800}

third_party/blink/web_tests/TestExpectations

@@ -266,10 +266,6 @@ crbug.com/926276 virtual/display-lock/wpt_internal/display-lock/lock-after-appen
 crbug.com/926276 virtual/display-lock/wpt_internal/display-lock/lock-after-append/nested-update-and-commit.html [ Timeout ]
 crbug.com/955533 virtual/display-lock/wpt_internal/display-lock/sizing/overflow-auto-with-overflow.html [ Failure ]
 
-# Render throttling
-crbug.com/520170 fast/dom/timer-throttling-hidden-page.html [ Failure Pass ]
-crbug.com/956354 fast/dom/timer-throttling-out-of-view-cross-origin-page.html [ Failure Pass ]
-
 # Sheriff 2018/05/25
 crbug.com/846747 http/tests/navigation/navigation-interrupted-by-fragment.html  [ Pass Timeout ]
 crbug.com/846747 virtual/stable/http/tests/navigation/navigation-interrupted-by-fragment.html  [ Pass Timeout ]
@@ -281,8 +277,6 @@ crbug.com/849459 fragmentation/repeating-thead-under-repeating-thead.html [ Fail
 Bug(none) http/tests/devtools/layers/layer-sticky-position-constraint-get.js [ Skip ]
 Bug(none) inspector-protocol/layers/get-layers.js [ Skip ]
 
-crbug.com/956354 http/tests/security/mixedContent/insecure-css-resources.html [ Pass Failure ]
-
 # Before we fully launch BlinkGenPropertyTrees, run visual/disable-blink-gen-property-trees/ on Linux.
 crbug.com/836884 [ Android ] virtual/disable-blink-gen-property-trees/ [ Skip ]
 crbug.com/836884 [ Win ] virtual/disable-blink-gen-property-trees/ [ Skip ]

third_party/blink/web_tests/fast/dom/timer-throttling-hidden-page-expected.txt

-Bug 98474: Throttle DOM timers on hidden pages and bug 400343 prerender pages.
+Bug 98474: Throttle DOM timers on hidden pages.
 
 On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
 
-
 PASS timerIntervalWhilePageVisible is within 20 of 100
 PASS firstTimerIntervalWhilePageNotVisible is >= 80
 PASS firstTimerIntervalWhilePageNotVisible <= 1120 is true
 PASS timerIntervalWhilePageNotVisible is within 20 of 1000
 PASS timerIntervalWhilePageVisible is within 20 of 100
 PASS timerIntervalWhilePageVisible is within 20 of 100
-PASS firstTimerIntervalWhilePageNotVisible is >= 80
-PASS firstTimerIntervalWhilePageNotVisible <= 1120 is true
-PASS timerIntervalWhilePageNotVisible is within 20 of 1000
-PASS timerIntervalWhilePageVisible is within 20 of 100
 PASS successfullyParsed is true
 
 TEST COMPLETE
-This test measures the time taken to fire a 100ms DOM Timer when the page visibility is set to "visible", "hidden", "visible", "prerender" and then back to "visible". Due to page timer throttling, the timer should fire close to 1s when page is hidden or prerender. And it should fire close to 100ms, when the page is visible.
+
+
+This test measures the time taken to fire a 100ms DOM Timer when the page visibility is set to "visible", "hidden", and then back to "visible". Due to page timer throttling, the timer should fire close to 1s when page is hidden. And it should fire close to 100ms, when the page is visible.