Add flag for disabling reclamation of unmodified wrappers

Will be used in a Finch experiment.

Bug: chromium:1107901
Change-Id: I68ea04be372ef2a931519c6d63916ed6001d7a26
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2312816
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Michael Lippautz <mlippautz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#790833}

gin/gin_features.cc

@@ -38,4 +38,8 @@ const base::Feature kV8FlushEmbeddedBlobICache{
 const base::Feature kV8ReduceConcurrentMarkingTasks{
     "V8ReduceConcurrentMarkingTasks", base::FEATURE_DISABLED_BY_DEFAULT};
 
+// Disables reclaiming of unmodified wrappers objects.
+const base::Feature kV8NoReclaimUnmodifiedWrappers{
+    "V8NoReclaimUnmodifiedWrappers", base::FEATURE_DISABLED_BY_DEFAULT};
+
 }  // namespace features

gin/gin_features.h

@@ -18,6 +18,7 @@ GIN_EXPORT extern const base::Feature kV8ConcurrentInlining;
 GIN_EXPORT extern const base::Feature kV8PerContextMarkingWorklist;
 GIN_EXPORT extern const base::Feature kV8FlushEmbeddedBlobICache;
 GIN_EXPORT extern const base::Feature kV8ReduceConcurrentMarkingTasks;
+GIN_EXPORT extern const base::Feature kV8NoReclaimUnmodifiedWrappers;
 
 }  // namespace features
 

gin/v8_initializer.cc

@@ -256,6 +256,13 @@ void V8Initializer::Initialize(IsolateHolder::ScriptMode mode) {
         sizeof(gc_experiment_reduce_concurrent_marking_tasks) - 1);
   }
 
+  if (base::FeatureList::IsEnabled(features::kV8NoReclaimUnmodifiedWrappers)) {
+    static constexpr char no_reclaim_unmodified_wrappers[] =
+        "--no-reclaim-unmodified-wrappers";
+    v8::V8::SetFlagsFromString(no_reclaim_unmodified_wrappers,
+                               sizeof(no_reclaim_unmodified_wrappers) - 1);
+  }
+
   if (IsolateHolder::kStrictMode == mode) {
     static const char use_strict[] = "--use_strict";
     v8::V8::SetFlagsFromString(use_strict, sizeof(use_strict) - 1);