gin: Remove the features flags of completed experiments

This removes
- V8MemoryReducerForSmallHeaps
- V8HugeMaxOldGenerationSize
- kV8GCBackgroundSchedule
- kV8GCLessCompaction
- kV8GCAlwaysPromoteYoungMC

Bug: 933107,958974,966832,1014943
Change-Id: Id7bebc72a0c8c6ecbb0ef2eb44339a0dcfbb5a4b
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2089758Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#747627}

gin/gin_features.cc

@@ -18,26 +18,6 @@ const base::Feature kV8FlushBytecode{"V8FlushBytecode",
 const base::Feature kV8LazyFeedbackAllocation{"V8LazyFeedbackAllocation",
                                               base::FEATURE_ENABLED_BY_DEFAULT};
 
-// Enables memory reducer for small heaps in V8.
-const base::Feature kV8MemoryReducerForSmallHeaps{
-    "V8MemoryReducerForSmallHeaps", base::FEATURE_ENABLED_BY_DEFAULT};
-
-// Increase V8 heap size to 4GB if the physical memory is bigger than 16 GB.
-const base::Feature kV8HugeMaxOldGenerationSize{
-    "V8HugeMaxOldGenerationSize", base::FEATURE_ENABLED_BY_DEFAULT};
-
-// Enables new background GC scheduling heuristics.
-const base::Feature kV8GCBackgroundSchedule{"V8GCBackgroundSchedule",
-                                            base::FEATURE_DISABLED_BY_DEFAULT};
-
-// Perform less compaction in non-memory reducing mode.
-const base::Feature kV8GCLessCompaction{"V8GCLessCompaction",
-                                        base::FEATURE_DISABLED_BY_DEFAULT};
-
-// Always promote young objects in Mark-Compact GC.
-const base::Feature kV8GCAlwaysPromoteYoungMC{
-    "V8GCAlwaysPromoteYoungMC", base::FEATURE_DISABLED_BY_DEFAULT};
-
 // Enable concurrent inlining in TurboFan.
 const base::Feature kV8ConcurrentInlining{"V8ConcurrentInlining",
                                           base::FEATURE_DISABLED_BY_DEFAULT};

gin/gin_features.h

@@ -13,11 +13,6 @@ namespace features {
 GIN_EXPORT extern const base::Feature kV8OptimizeJavascript;
 GIN_EXPORT extern const base::Feature kV8FlushBytecode;
 GIN_EXPORT extern const base::Feature kV8LazyFeedbackAllocation;
-GIN_EXPORT extern const base::Feature kV8MemoryReducerForSmallHeaps;
-GIN_EXPORT extern const base::Feature kV8HugeMaxOldGenerationSize;
-GIN_EXPORT extern const base::Feature kV8GCBackgroundSchedule;
-GIN_EXPORT extern const base::Feature kV8GCLessCompaction;
-GIN_EXPORT extern const base::Feature kV8GCAlwaysPromoteYoungMC;
 GIN_EXPORT extern const base::Feature kV8ConcurrentInlining;
 
 }  // namespace features

gin/v8_initializer.cc

@@ -218,42 +218,6 @@ void V8Initializer::Initialize(IsolateHolder::ScriptMode mode) {
                                sizeof(no_lazy_feedback_allocation) - 1);
   }
 
-  if (!base::FeatureList::IsEnabled(features::kV8MemoryReducerForSmallHeaps)) {
-    static const char no_memory_reducer[] =
-        "--no-memory-reducer-for-small-heaps";
-    v8::V8::SetFlagsFromString(no_memory_reducer,
-                               sizeof(no_memory_reducer) - 1);
-  }
-
-  if (base::FeatureList::IsEnabled(features::kV8HugeMaxOldGenerationSize)) {
-    static const char huge_max_old_generation_size[] =
-        "--huge_max_old_generation_size";
-    v8::V8::SetFlagsFromString(huge_max_old_generation_size,
-                               sizeof(huge_max_old_generation_size) - 1);
-  }
-
-  if (base::FeatureList::IsEnabled(features::kV8GCBackgroundSchedule)) {
-    static const char gc_experiment_background_schedule[] =
-        "--gc_experiment_background_schedule";
-    v8::V8::SetFlagsFromString(gc_experiment_background_schedule,
-                               sizeof(gc_experiment_background_schedule) - 1);
-  }
-
-  if (base::FeatureList::IsEnabled(features::kV8GCLessCompaction)) {
-    static const char gc_experiment_less_compaction[] =
-        "--gc_experiment_less_compaction";
-    v8::V8::SetFlagsFromString(gc_experiment_less_compaction,
-                               sizeof(gc_experiment_less_compaction) - 1);
-  }
-
-  if (base::FeatureList::IsEnabled(features::kV8GCAlwaysPromoteYoungMC)) {
-    static const char gc_experiment_always_promote_young_mc[] =
-        "--always_promote_young_mc";
-    v8::V8::SetFlagsFromString(
-        gc_experiment_always_promote_young_mc,
-        sizeof(gc_experiment_always_promote_young_mc) - 1);
-  }
-
   if (base::FeatureList::IsEnabled(features::kV8ConcurrentInlining)) {
     static const char tf_experiment_concurrent_inlining[] =
         "--concurrent_inlining";