fieldtrial: Enable V8's --idle-gc-on-context-disposal

Bug: chromium:333423696
Change-Id: I8082668bbdab45cc7aebd517674cf0706e202966
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/5464468
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Reviewed-by: Omer Katz <omerkatz@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1291319}

gin/gin_features.cc

@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "gin/gin_features.h"
+
 #include "base/metrics/field_trial_params.h"
 
 namespace features {
@@ -211,6 +212,10 @@ BASE_FEATURE(kV8UseOriginalMessageForStackTrace,
              "V8UseOriginalMessageForStackTrace",
              base::FEATURE_ENABLED_BY_DEFAULT);
 
+BASE_FEATURE(kV8IdleGcOnContextDisposal,
+             "V8IdleGcOnContextDisposal",
+             base::FEATURE_ENABLED_BY_DEFAULT);
+
 // Elide redundant TDZ hole checks in bytecode. This only sets the V8 flag when
 // manually overridden.
 BASE_FEATURE(kV8IgnitionElideRedundantTdzChecks,

gin/gin_features.h

@@ -30,6 +30,7 @@ GIN_EXPORT BASE_DECLARE_FEATURE(kV8FlushCodeBasedOnTabVisibility);
 GIN_EXPORT BASE_DECLARE_FEATURE(kV8FlushCodeBasedOnTime);
 GIN_EXPORT extern const base::FeatureParam<int> kV8FlushCodeOldTime;
 GIN_EXPORT BASE_DECLARE_FEATURE(kV8FlushEmbeddedBlobICache);
+GIN_EXPORT BASE_DECLARE_FEATURE(kV8IdleGcOnContextDisposal);
 GIN_EXPORT BASE_DECLARE_FEATURE(kV8IgnitionElideRedundantTdzChecks);
 GIN_EXPORT BASE_DECLARE_FEATURE(kV8IntelJCCErratumMitigation);
 GIN_EXPORT BASE_DECLARE_FEATURE(kV8LazyFeedbackAllocation);

gin/v8_initializer.cc

@@ -283,6 +283,9 @@ void SetFlags(IsolateHolder::ScriptMode mode,
     SetV8FlagsFormatted("--memory-reducer-gc-count=%i",
                         features::kV8MemoryReducerGCCount.Get());
   }
+  SetV8FlagsIfOverridden(features::kV8IdleGcOnContextDisposal,
+                         "--idle-gc-on-context-disposal",
+                         "--no-idle-gc-on-context-disposal");
   SetV8FlagsIfOverridden(features::kV8MinorMS, "--minor-ms", "--no-minor-ms");
   SetV8FlagsIfOverridden(features::kV8Sparkplug, "--sparkplug",
                          "--no-sparkplug");

testing/variations/fieldtrial_testing_config.json

@@ -20851,6 +20851,28 @@
             ]
         }
     ],
+    "V8IdleGcOnContextDisposal": [
+        {
+            "platforms": [
+                "android",
+                "android_webview",
+                "chromeos",
+                "chromeos_lacros",
+                "fuchsia",
+                "linux",
+                "mac",
+                "windows"
+            ],
+            "experiments": [
+                {
+                    "name": "Enabled",
+                    "enable_features": [
+                        "V8IdleGcOnContextDisposal"
+                    ]
+                }
+            ]
+        }
+    ],
     "V8IntelJCCErratumMitigation": [
         {
             "platforms": [