Revert "Add PerfectHeuristics UKM event, and metric for DelayAsyncScriptExecution"

This reverts commit 647d93e9.

Reason for revert: crbug/1116821 - causing crashes
TBR=ryansturm@chromium.org,falken@chromium.org,rkaplow@chromium.org

Original change's description:
> Add PerfectHeuristics UKM event, and metric for DelayAsyncScriptExecution
>
> This CL introduces the PerfectHeuristics UKM event, along with a boolean
> metric for when a blink::ScriptRunner comes across an async script
> before the script element's node document has finished parsing. The
> PerfectHeuristics UKM event is logged in the UkmPageLoadMetricsObserver.
>
> See the Google-internal UKM privacy review:
> https://docs.google.com/document/d/1UqkpGXc4LEh5jzzVR8fCVVTuCuG2mwvhQTuCy36zT3g/edit#
>
> See the Perfect Heuristics [1] project document (currently
> Google-internal).
>
> [1]: https://docs.google.com/document/d/1Y7uF76Gq0VlJZky2j7x-lbD1_awH64eW0WRg1bNLuFs/edit
>
> R=​falken@chromium.org, nhiroki@chromium.org, ryansturm@chromium.org, sophiechang@chromium.org
>
> Bug: 1086227
> Change-Id: I71954491a1a559c2e1244a543092f1b8f38b8136
> Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2340845
> Commit-Queue: Dominic Farolino <dom@chromium.org>
> Reviewed-by: Sophie Chang <sophiechang@chromium.org>
> Reviewed-by: Ryan Sturm <ryansturm@chromium.org>
> Reviewed-by: Matt Falkenhagen <falken@chromium.org>
> Reviewed-by: Hiroki Nakagawa <nhiroki@chromium.org>
> Reviewed-by: Robert Kaplow <rkaplow@chromium.org>
> Cr-Commit-Position: refs/heads/master@{#798393}

TBR=falken@chromium.org,rkaplow@chromium.org,nhiroki@chromium.org,sophiechang@chromium.org,ryansturm@chromium.org,dom@chromium.org

# Not skipping CQ checks because original CL landed > 1 day ago.

Bug: 1086227,1116821
Change-Id: I0131884d123e2122fa674097381293174795fecf
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2359573
Commit-Queue: Sophie Chang <sophiechang@chromium.org>
Reviewed-by: Sophie Chang <sophiechang@chromium.org>
Cr-Commit-Position: refs/heads/master@{#798738}

chrome/browser/page_load_metrics/observers/ukm_page_load_metrics_observer.cc

@@ -319,7 +319,6 @@ void UkmPageLoadMetricsObserver::OnComplete(
     RecordInputTimingMetrics();
   }
   ReportLayoutStability();
-  ReportPerfectHeuristicsMetrics();
   ReportAbortMetrics(timing, current_time);
 }
 
@@ -878,15 +877,6 @@ void UkmPageLoadMetricsObserver::ReportLayoutStability() {
   }
 }
 
-void UkmPageLoadMetricsObserver::ReportPerfectHeuristicsMetrics() {
-  ukm::builders::PerfectHeuristics builder(GetDelegate().GetPageUkmSourceId());
-  if (!delay_async_script_execution_before_finished_parsing_seen_)
-    return;
-
-  builder.Setdelay_async_script_execution_before_finished_parsing(1).Record(
-      ukm::UkmRecorder::Get());
-}
-
 void UkmPageLoadMetricsObserver::ReportAbortMetrics(
     const page_load_metrics::mojom::PageLoadTiming& timing,
     base::TimeTicks page_end_time) {
@@ -1154,10 +1144,4 @@ void UkmPageLoadMetricsObserver::OnLoadingBehaviorObserved(
                           kLoadingBehaviorFontPreloadStartedBeforeRendering) {
     font_preload_started_before_rendering_observed_ = true;
   }
-
-  if (behavior_flag &
-      blink::LoadingBehaviorFlag::
-          kLoadingBehaviorAsyncScriptReadyBeforeDocumentFinishedParsing) {
-    delay_async_script_execution_before_finished_parsing_seen_ = true;
-  }
 }

chrome/browser/page_load_metrics/observers/ukm_page_load_metrics_observer.h

@@ -142,8 +142,6 @@ class UkmPageLoadMetricsObserver
 
   void ReportLayoutStability();
 
-  void ReportPerfectHeuristicsMetrics();
-
   void ReportAbortMetrics(
       const page_load_metrics::mojom::PageLoadTiming& timing,
       base::TimeTicks page_end_time);
@@ -250,9 +248,7 @@ class UkmPageLoadMetricsObserver
   // Unique across the lifetime of the browser process.
   int main_document_sequence_number_ = -1;
 
-  // These are to capture observed LoadingBehaviorFlags.
   bool font_preload_started_before_rendering_observed_ = false;
-  bool delay_async_script_execution_before_finished_parsing_seen_ = false;
 
   bool currently_in_foreground_ = false;
   // The last time the page became foregrounded, or navigation start if the page

chrome/browser/page_load_metrics/observers/ukm_page_load_metrics_observer_unittest.cc

@@ -1461,28 +1461,6 @@ TEST_F(UkmPageLoadMetricsObserverTest,
               testing::ElementsAre(base::Bucket(25, 1)));
 }
 
-TEST_F(UkmPageLoadMetricsObserverTest,
-       PerfectHeuristicsDelayaAsyncScriptExecution) {
-  NavigateAndCommit(GURL(kTestUrl1));
-
-  page_load_metrics::mojom::FrameMetadata metadata;
-  metadata.behavior_flags |= blink::LoadingBehaviorFlag::
-      kLoadingBehaviorAsyncScriptReadyBeforeDocumentFinishedParsing;
-  tester()->SimulateMetadataUpdate(metadata, web_contents()->GetMainFrame());
-
-  // Simulate closing the tab.
-  DeleteContents();
-
-  auto entries = tester()->test_ukm_recorder().GetEntriesByName(
-      ukm::builders::PerfectHeuristics::kEntryName);
-  EXPECT_EQ(1ul, entries.size());
-  tester()->test_ukm_recorder().ExpectEntryMetric(
-      entries.front(),
-      ukm::builders::PerfectHeuristics::
-          kdelay_async_script_execution_before_finished_parsingName,
-      1);
-}
-
 TEST_F(UkmPageLoadMetricsObserverTest, MHTMLNotTracked) {
   auto navigation = content::NavigationSimulator::CreateBrowserInitiated(
       GURL(kTestUrl1), web_contents());

third_party/blink/public/common/loader/loading_behavior_flag.h

@@ -44,9 +44,6 @@ enum LoadingBehaviorFlag {
   // Indicates that the page uses the Next.js JavaScript framework (via a
   // window variable)
   kLoadingBehaviorNextJSFrameworkUsed = 1 << 9,
-  // Indicates that an async script was ready to execute before the script
-  // element's node document has finished parsing.
-  kLoadingBehaviorAsyncScriptReadyBeforeDocumentFinishedParsing = 1 << 10,
 };
 
 }  // namespace blink

third_party/blink/renderer/core/script/script_runner.cc

@@ -32,7 +32,6 @@
 #include "third_party/blink/public/platform/task_type.h"
 #include "third_party/blink/renderer/core/dom/document.h"
 #include "third_party/blink/renderer/core/frame/local_dom_window.h"
-#include "third_party/blink/renderer/core/loader/document_loader.h"
 #include "third_party/blink/renderer/core/script/script_loader.h"
 #include "third_party/blink/renderer/platform/heap/handle.h"
 #include "third_party/blink/renderer/platform/runtime_enabled_features.h"
@@ -148,10 +147,6 @@ bool ScriptRunner::CanDelayAsyncScripts() {
           DelayAsyncScriptExecutionUntilFinishedParsingEnabled() ||
       RuntimeEnabledFeatures::
           DelayAsyncScriptExecutionUntilFirstPaintOrFinishedParsingEnabled();
-  if (!document_->Parsing()) {
-    document_->Loader()->DidObserveLoadingBehavior(
-        kLoadingBehaviorAsyncScriptReadyBeforeDocumentFinishedParsing);
-  }
   return !delay_async_script_milestone_reached_ && flags_enabled;
 }
 

tools/metrics/ukm/ukm.xml

@@ -9606,21 +9606,6 @@ be describing additional metrics about the same event.
   </summary>
 </event>
 
-<event name="PerfectHeuristics" singular="True">
-  <owner>dom@chromium.org</owner>
-  <owner>chrome-loading@google.com</owner>
-  <summary>
-    Metrics recorded for the various Perfect Heuristics experiments being run.
-  </summary>
-  <metric name="delay_async_script_execution_before_finished_parsing"
-      enum="Boolean">
-    <summary>
-      Set to 1 when blink::ScriptRunner sees an async script before the
-      associated document has finished parsing.
-    </summary>
-  </metric>
-</event>
-
 <event name="PeriodicBackgroundSyncEventCompleted">
   <owner>nator@chromium.org</owner>
   <owner>rayankans@chromium.org</owner>