BackupRefPtrAndPCScan & PartitionAllocEverywhere experiments

Bring back synthetic PartitionAllocEverywhere experiment, scheduled for
1/8.

Also add synthetic BackupRefPtrAndPCScan experiment, scheduled for 1/12.
This requires disabling PCScan when BackupRefPtr is in use.

Bug: 1073933, 11297512
Change-Id: I5a575c4d60ff6d6eb196e0508851f279ce1fb7c7
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2612307Reviewed-by: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: Yuki Shiino <yukishiino@chromium.org>
Reviewed-by: Kentaro Hara <haraken@chromium.org>
Reviewed-by: Anton Bikineev <bikineev@chromium.org>
Commit-Queue: Bartek Nowierski <bartekn@chromium.org>
Cr-Commit-Position: refs/heads/master@{#840943}

base/allocator/partition_allocator/partition_alloc_features.h

@@ -6,6 +6,7 @@
 #define BASE_ALLOCATOR_PARTITION_ALLOCATOR_PARTITION_ALLOC_FEATURES_H_
 
 #include "base/allocator/buildflags.h"
+#include "base/allocator/partition_allocator/checked_ptr_support.h"
 #include "base/allocator/partition_allocator/partition_alloc_constants.h"
 #include "base/base_export.h"
 #include "base/feature_list.h"
@@ -64,7 +65,7 @@ ALWAYS_INLINE bool IsPartitionAllocGigaCageEnabled() {
 }
 
 ALWAYS_INLINE bool IsPartitionAllocPCScanEnabled() {
-#if defined(PA_HAS_64_BITS_POINTERS)
+#if defined(PA_HAS_64_BITS_POINTERS) && !ENABLE_REF_COUNT_FOR_BACKUP_REF_PTR
   return FeatureList::IsEnabled(kPartitionAllocPCScan);
 #else  // PA_HAS_64_BITS_POINTERS
   return false;
@@ -73,7 +74,7 @@ ALWAYS_INLINE bool IsPartitionAllocPCScanEnabled() {
 
 #if BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
 ALWAYS_INLINE bool IsPartitionAllocPCScanBrowserOnlyEnabled() {
-#if defined(PA_HAS_64_BITS_POINTERS)
+#if defined(PA_HAS_64_BITS_POINTERS) && !ENABLE_REF_COUNT_FOR_BACKUP_REF_PTR
   return FeatureList::IsEnabled(kPartitionAllocPCScanBrowserOnly);
 #else  // PA_HAS_64_BITS_POINTERS
   return false;

base/allocator/partition_allocator/partition_root.cc

@@ -4,6 +4,7 @@
 
 #include "base/allocator/partition_allocator/partition_root.h"
 
+#include "base/allocator/partition_allocator/checked_ptr_support.h"
 #include "base/allocator/partition_allocator/oom.h"
 #include "base/allocator/partition_allocator/page_allocator.h"
 #include "base/allocator/partition_allocator/partition_alloc_check.h"
@@ -27,7 +28,7 @@ typename PartitionRoot<thread_safe>::PCScanMode PartitionOptionsToPCScanMode(
   // PCScan is currently only supported on 64-bit systems.
   // Mark partitions non-scannable on 32-bit systems unconditionally, so that
   // address space for quarantine bitmaps doesn't get reserved.
-#if defined(PA_HAS_64_BITS_POINTERS)
+#if defined(PA_HAS_64_BITS_POINTERS) && !ENABLE_REF_COUNT_FOR_BACKUP_REF_PTR
   switch (opt) {
     case PartitionOptions::PCScan::kAlwaysDisabled:
       return Root::PCScanMode::kNonScannable;

chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc

@@ -7,6 +7,7 @@
 #include <cmath>
 #include <string>
 
+#include "base/allocator/partition_allocator/checked_ptr_support.h"
 #include "base/allocator/partition_allocator/partition_alloc_features.h"
 #include "base/bind.h"
 #include "base/command_line.h"
@@ -547,18 +548,29 @@ void ChromeBrowserMainExtraPartsMetrics::PreBrowserStart() {
 
 #endif  // defined(OS_WIN)
 
-  // Records whether or not PartitionAlloc is used as the default allocator,
-  // plus whether or not PCScan is enabled.
+  // Records whether or not PartitionAlloc is used as the default allocator.
   ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
-      "PartitionAllocEverywhereAndPCScan",
+      "PartitionAllocEverywhere",
 #if BUILDFLAG(USE_PARTITION_ALLOC_EVERYWHERE)
-      base::features::IsPartitionAllocPCScanBrowserOnlyEnabled()
-          ? "EnabledWithPCScan"
-          : "EnabledWithoutPCScan"
+      "Enabled"
 #else
       "Disabled"
 #endif
   );
+
+#if defined(OS_WIN) && BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
+  // Records whether or not BackupRefPtr and/or PCScan is enabled.
+  ChromeMetricsServiceAccessor::RegisterSyntheticFieldTrial(
+      "BackupRefPtrAndPCScan",
+#if ENABLE_REF_COUNT_FOR_BACKUP_REF_PTR
+      "BackupRefPtrEnabled"
+#else
+      base::features::IsPartitionAllocPCScanBrowserOnlyEnabled()
+          ? "PCScanEnabled"
+          : "Disabled"
+#endif
+  );
+#endif  // defined(OS_WIN) && BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
 }
 
 void ChromeBrowserMainExtraPartsMetrics::PostBrowserStart() {

third_party/blink/renderer/platform/wtf/allocator/partitions.cc

@@ -30,6 +30,7 @@
 
 #include "third_party/blink/renderer/platform/wtf/allocator/partitions.h"
 
+#include "base/allocator/partition_allocator/checked_ptr_support.h"
 #include "base/allocator/partition_allocator/memory_reclaimer.h"
 #include "base/allocator/partition_allocator/oom.h"
 #include "base/allocator/partition_allocator/page_allocator.h"
@@ -102,6 +103,7 @@ bool Partitions::InitializeOnce() {
   buffer_root_ = buffer_allocator->root();
   layout_root_ = layout_allocator->root();
 
+#if !ENABLE_REF_COUNT_FOR_BACKUP_REF_PTR
   if (base::features::IsPartitionAllocPCScanEnabled() ||
       base::FeatureList::IsEnabled(kPCScanBlinkPartitions)) {
 #if !BUILDFLAG(USE_PARTITION_ALLOC_AS_MALLOC)
@@ -109,6 +111,7 @@ bool Partitions::InitializeOnce() {
 #endif
     buffer_root_->EnablePCScan();
   }
+#endif
 
   initialized_ = true;
   return initialized_;