[blink scheduler] Cleanup the OptOutZeroTimeoutTimersFromThrottling feature.

Experiment results:
https://docs.google.com/document/d/1Fpq31rNHiMHorCygu_1krpIun_0J1ePfef6lf1l4PLA/edit?usp=sharing

Bug: 1075553
Change-Id: I63b893fb7e4fef9269d498c03f95b4cd201133b1
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2568213Reviewed-by: Alexander Timin <altimin@chromium.org>
Reviewed-by: Chris Harrelson <chrishtr@chromium.org>
Commit-Queue: François Doray <fdoray@chromium.org>
Cr-Commit-Position: refs/heads/master@{#833295}

third_party/blink/common/features.cc

@@ -273,10 +273,6 @@ const base::Feature kWebRtcIgnoreUnspecifiedColorSpace{
 const base::Feature kIntensiveWakeUpThrottling{
     "IntensiveWakeUpThrottling", base::FEATURE_DISABLED_BY_DEFAULT};
 
-// When enabled, timers with timeout=0 are not throttled.
-const base::Feature kOptOutZeroTimeoutTimersFromThrottling{
-    "OptOutZeroTimeoutTimersFromThrottling", base::FEATURE_ENABLED_BY_DEFAULT};
-
 // Name of the parameter that controls the grace period during which there is no
 // intensive wake up throttling after a page is hidden. Defined here to allow
 // access from about_flags.cc. The FeatureParam is defined in

third_party/blink/public/common/features.h

@@ -79,9 +79,6 @@ BLINK_COMMON_EXPORT extern const base::Feature kIntensiveWakeUpThrottling;
 BLINK_COMMON_EXPORT extern const char
     kIntensiveWakeUpThrottling_GracePeriodSeconds_Name[];
 
-BLINK_COMMON_EXPORT extern const base::Feature
-    kOptOutZeroTimeoutTimersFromThrottling;
-
 #if BUILDFLAG(RTC_USE_H264) && BUILDFLAG(ENABLE_FFMPEG_VIDEO_DECODERS)
 BLINK_COMMON_EXPORT extern const base::Feature kWebRtcH264WithOpenH264FFmpeg;
 #endif  // BUILDFLAG(RTC_USE_H264) && BUILDFLAG(ENABLE_FFMPEG_VIDEO_DECODERS)

third_party/blink/public/platform/TaskTypes.md

@@ -19,9 +19,9 @@ pausable. Some internal task queues are not.
 | MediaElementEvent                 | No          | No                      |  No        | Yes       | Yes      | Yes          |
 | CanvasBlobSerialization           | No          | No                      |  Yes       | Yes       | Yes      | Yes          |
 | Microtask                         | No          | No                      |  Yes       | Yes       | Yes      | Yes          |
-| JavascriptTimerDelayedLowNesting  | Yes         | No [^2]                 |  Yes       | Yes       | Yes      | Yes          |
-| JavascriptTimerDelayedHighNesting | Yes         | Yes [^3]                |  Yes       | Yes       | Yes      | Yes          |
-| JavascriptTimerImmediate          | No [^1]     | No                      |  Yes       | Yes       | Yes      | Yes          |
+| JavascriptTimerDelayedLowNesting  | Yes         | No [^1]                 |  Yes       | Yes       | Yes      | Yes          |
+| JavascriptTimerDelayedHighNesting | Yes         | Yes [^2]                |  Yes       | Yes       | Yes      | Yes          |
+| JavascriptTimerImmediate          | No          | No                      |  Yes       | Yes       | Yes      | Yes          |
 | RemoteEvent                       | No          | No                      |  Yes       | Yes       | Yes      | Yes          |
 | WebSocket                         | No          | No                      |  Yes       | Yes       | Yes      | Yes          |
 | PostedMessage                     | No          | No                      |  No        | Yes       | Yes      | Yes          |
@@ -63,9 +63,7 @@ Internal Translation queue supports concept of it running only in the foreground
 has been backgrounded for 5 minutes. See
 [Chrome Platform Status entry](https://www.chromestatus.com/feature/4718288976216064).
 
-[^1] "Yes" if the "OptOutZeroTimeoutTimersFromThrottling" feature is disabled.
-
-[^2] "Yes" if the "IntensiveWakeUpThrottling" feature is enabled and the
+[^1] "Yes" if the "IntensiveWakeUpThrottling" feature is enabled and the
 "can_intensively_throttle_low_nesting_level" param is "true".
 
-[^3] "No" if the "IntensiveWakeUpThrottling" feature is disabled.
+[^2] "No" if the "IntensiveWakeUpThrottling" feature is disabled.

third_party/blink/renderer/core/scheduler_integration_tests/throttling_test.cc

@@ -139,63 +139,11 @@ TEST_F(BackgroundPageThrottlingTest, TimersThrottledInBackgroundPage) {
               ElementsAre(console_message, console_message, console_message));
 }
 
-// Verify that a timer with timeout=0 is not throttled until its timeout is
-// rounded up to 4ms.
-TEST_F(BackgroundPageThrottlingTest,
-       ZeroTimeoutTimersThrottledInBackgroundPage) {
-  SimRequest main_resource("https://example.com/", "text/html");
-
-  LoadURL("https://example.com/");
-
-  const String console_message = BuildTimerConsoleMessage();
-  main_resource.Complete(
-      String::Format("(<script>"
-                     "  function f(repetitions) {"
-                     "     if (repetitions == 0) return;"
-                     "     console.log('%s');"
-                     "     setTimeout(f, 0, repetitions - 1);"
-                     "  }"
-                     "  setTimeout(f, 0, 50);"
-                     "</script>)",
-                     console_message.Utf8().c_str()));
-
-  GetDocument().GetPage()->GetPageScheduler()->SetPageVisible(false);
-
-  // Initially, timeout is rounded up to 1ms and no throttling is applied
-  // (https://crbug.com/402694). After 4 executions, timeout is rounded up to
-  // 4ms and throttling is applied.
-  constexpr base::TimeDelta k10Ms = base::TimeDelta::FromMilliseconds(10);
-  platform_->RunForPeriod(k10Ms);
-  EXPECT_THAT(FilteredConsoleMessages(),
-              ElementsAre(console_message, console_message, console_message,
-                          console_message));
-  platform_->RunForPeriod(base::TimeDelta::FromSeconds(1) - k10Ms);
-  EXPECT_THAT(FilteredConsoleMessages(),
-              ElementsAre(console_message, console_message, console_message,
-                          console_message, console_message));
-}
-
-namespace {
-
-class OptOutZeroTimeoutFromThrottlingTest : public ThrottlingTestBase {
- public:
-  OptOutZeroTimeoutFromThrottlingTest() {
-    scoped_feature_list_.InitAndEnableFeature(
-        features::kOptOutZeroTimeoutTimersFromThrottling);
-  }
-
- private:
-  base::test::ScopedFeatureList scoped_feature_list_;
-};
-
-}  // namespace
-
-// Verify that in a hidden page, when the kOptOutZeroTimeoutTimersFromThrottling
-// feature is enabled:
+// Verify the execution time of non-nested timers on a hidden page.
 // - setTimeout(..., 0) and setTimeout(..., -1) schedule their callback after
 //   1ms. The 1 ms delay exists for historical reasons crbug.com/402694.
 // - setTimeout(..., 5) schedules its callback at the next aligned time
-TEST_F(OptOutZeroTimeoutFromThrottlingTest, WithoutNesting) {
+TEST_F(BackgroundPageThrottlingTest, WithoutNesting) {
   SimRequest main_resource("https://example.com/", "text/html");
   LoadURL("https://example.com/");
 
@@ -228,10 +176,9 @@ TEST_F(OptOutZeroTimeoutFromThrottlingTest, WithoutNesting) {
                           timeout_5_message));
 }
 
-// Verify that in a hidden page, when the kOptOutZeroTimeoutTimersFromThrottling
-// feature is enabled, a timer created with setTimeout(..., 0) is throttled
-// after 5 nesting levels.
-TEST_F(OptOutZeroTimeoutFromThrottlingTest, SetTimeoutNesting) {
+// Verify that on a hidden page, a timer created with setTimeout(..., 0) is
+// throttled after 5 nesting levels.
+TEST_F(BackgroundPageThrottlingTest, NestedSetTimeoutZero) {
   SimRequest main_resource("https://example.com/", "text/html");
   LoadURL("https://example.com/");
 
@@ -262,10 +209,9 @@ TEST_F(OptOutZeroTimeoutFromThrottlingTest, SetTimeoutNesting) {
   EXPECT_THAT(FilteredConsoleMessages(), Vector<String>(5, console_message));
 }
 
-// Verify that in a hidden page, when the kOptOutZeroTimeoutTimersFromThrottling
-// feature is enabled, a timer created with setInterval(..., 0) is throttled
-// after 5 nesting levels.
-TEST_F(OptOutZeroTimeoutFromThrottlingTest, SetIntervalNesting) {
+// Verify that in a hidden page, a timer created with setInterval(..., 0) is
+// throttled after 5 nesting levels.
+TEST_F(BackgroundPageThrottlingTest, NestedSetIntervalZero) {
   SimRequest main_resource("https://example.com/", "text/html");
   LoadURL("https://example.com/");
 

third_party/blink/renderer/platform/scheduler/main_thread/frame_scheduler_impl.cc

@@ -384,11 +384,9 @@ QueueTraits FrameSchedulerImpl::CreateQueueTraitsForTaskType(TaskType type) {
               QueueTraits::PrioritisationType::kJavaScriptTimer)
           .SetCanBeIntensivelyThrottled(IsIntensiveWakeUpThrottlingEnabled());
     case TaskType::kJavascriptTimerImmediate: {
-      return DeferrableTaskQueueTraits()
-          .SetPrioritisationType(
-              QueueTraits::PrioritisationType::kJavaScriptTimer)
-          .SetCanBeThrottled(!base::FeatureList::IsEnabled(
-              features::kOptOutZeroTimeoutTimersFromThrottling));
+      // Immediate timers are not throttled.
+      return DeferrableTaskQueueTraits().SetPrioritisationType(
+          QueueTraits::PrioritisationType::kJavaScriptTimer);
     }
     case TaskType::kInternalLoading:
     case TaskType::kNetworking: