[cr149] Fixes BraveWindowTracker dangling pointer.

BraveWindowTracker is initialized in
BraveBrowserMainExtraParts::PreMainMessageLoopRun. It uses
base::ScopedObservation<BrowserCollection, BrowserCollectionObserver>,
which obseves browser collection which goes out of scope with
GlobalFeatures. BraveWindowTracker needs to stop observing before then.

Added HasInstance/ClearInstance to BraveWindowTracker modeling this
behavior on upstream's ChromeBrowserMainExtraPartsMetrics and
metrics::TabStatsTracker.

[33240:46492:0417/173936.000:ERROR:base\allocator\partition_alloc_support.cc:683] A freed allocation is still referenced by a dangling pointer at exit, or at test end. Leaked raw_ptr/raw_ref could cause PartitionAlloc's quarantine memory bloat.

Memory was released on:
        brave_browser_tests!base::allocator::`anonymous namespace'::DanglingRawPtrDetected [0x7ff7130f09ee+3ee] (base\allocator\partition_alloc_support.cc:438)
        brave_browser_tests!GlobalFeatures::~GlobalFeatures [0x7ff711aec13d+cd] (chrome\browser\global_features.cc:96)
        brave_browser_tests!BraveGlobalFeatures::~BraveGlobalFeatures [0x7ff710d19780+10] (brave\browser\brave_global_features.cc:12)
        brave_browser_tests!BrowserProcessImpl::~BrowserProcessImpl [0x7ff711b8ccb8+138] (chrome\browser\browser_process_impl.cc:565)
        brave_browser_tests!BraveBrowserProcessImpl::~BraveBrowserProcessImpl [0x7ff711b46128+3c8] (brave\browser\brave_browser_process_impl.cc:142)
        brave_browser_tests!BraveBrowserProcessImpl::~BraveBrowserProcessImpl [0x7ff711b47fa0+10] (brave\browser\brave_browser_process_impl.cc:142)
        brave_browser_tests!ChromeBrowserMainParts_ChromiumImpl::PostDestroyThreads [0x7ff711b52658+168] (chrome\browser\chrome_browser_main.cc:2291)
        brave_browser_tests!content::BrowserMainLoop::ShutdownThreadsAndCleanUp [0x7ff70d2638c7+7b7] (content\browser\browser_main_loop.cc:1282)
        brave_browser_tests!content::BrowserMainRunnerImpl::Shutdown [0x7ff70d265b86+106] (content\browser\browser_main_runner_impl.cc:177)

ERROR:base\allocator\partition_alloc_support.cc:700] Dangling reference from:
ERROR:base\allocator\partition_alloc_support.cc:701]      brave_browser_tests!partition_alloc::internal::base::debug::CollectStackTrace [0x7ff713271b82+12] (base\allocator\partition_allocator\src\partition_alloc\partition_alloc_base\debug\stack_trace_win.cc:103)
        brave_browser_tests!base::internal::InstanceTracer::TraceImpl [0x7ff7132712ee+1fe] (base\allocator\partition_allocator\src\partition_alloc\pointers\instance_tracer.cc:66)
        brave_browser_tests!base::ScopedObservation<brave_rewards::RewardsService,brave_rewards::RewardsServiceObserver,0>::Observe [0x7ff707af12d8+128] (base\scoped_observation.h:117)
        brave_browser_tests!brave::BraveWindowTracker::BraveWindowTracker [0x7ff7119c682d+11d] (brave\browser\p3a\p3a_core_metrics.cc:60)
        brave_browser_tests!brave::BraveWindowTracker::CreateInstance [0x7ff7119c6de1+21] (brave\browser\p3a\p3a_core_metrics.cc:71)
        brave_browser_tests!BraveBrowserMainExtraParts::PreMainMessageLoopRun [0x7ff711a00915+185] (brave\browser\brave_browser_main_extra_parts.cc:104)
        brave_browser_tests!ChromeBrowserMainParts_ChromiumImpl::PreMainMessageLoopRun [0x7ff711b4fd60+60] (chrome\browser\chrome_browser_main.cc:1465)

browser/brave_browser_main_extra_parts.cc

@@ -51,8 +51,9 @@ void RecordInitialP3AValues() {
                                             g_browser_process->local_state());
 
   // Record crash reporting status stats.
-  const bool crash_reports_enabled = g_browser_process->local_state()->
-      GetBoolean(metrics::prefs::kMetricsReportingEnabled);
+  const bool crash_reports_enabled =
+      g_browser_process->local_state()->GetBoolean(
+          metrics::prefs::kMetricsReportingEnabled);
   UMA_HISTOGRAM_BOOLEAN("Brave.Core.CrashReportsEnabled",
                         crash_reports_enabled);
 }
@@ -105,3 +106,14 @@ void BraveBrowserMainExtraParts::PreMainMessageLoopRun() {
 #endif  // !BUILDFLAG(IS_ANDROID)
   g_brave_browser_process->process_misc_metrics()->uptime_monitor()->Init();
 }
+
+void BraveBrowserMainExtraParts::PostDestroyThreads() {
+#if !BUILDFLAG(IS_ANDROID)
+  // Based on chrome/browser/metrics/chrome_browser_main_extra_parts_metrics.cc
+  // The instance needs to delete itself as it uses BrowserCollection observer
+  // and the collection will go out of scope with the browser process.
+  if (brave::BraveWindowTracker::HasInstance()) {
+    brave::BraveWindowTracker::ClearInstance();
+  }
+#endif  // !BUILDFLAG(IS_ANDROID)
+}

browser/brave_browser_main_extra_parts.h

@@ -22,6 +22,7 @@ class BraveBrowserMainExtraParts : public ChromeBrowserMainExtraParts {
   void PostBrowserStart() override;
   void PreMainMessageLoopRun() override;
   void PreProfileInit() override;
+  void PostDestroyThreads() override;
 };
 
 #endif  // BRAVE_BROWSER_BRAVE_BROWSER_MAIN_EXTRA_PARTS_H_

browser/p3a/p3a_core_metrics.cc

@@ -1,7 +1,7 @@
-/* Copyright 2019 The Brave Authors. All rights reserved.
+/* Copyright (c) 2019 The Brave Authors. All rights reserved.
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
+ * You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 #include "brave/browser/p3a/p3a_core_metrics.h"
 
@@ -42,8 +42,7 @@ enum class WindowUsageStats {
 };
 
 const char* GetPrefNameForProfile(Profile* profile) {
-  if (profile->IsIncognitoProfile() &&
-      !profile->IsTor()) {
+  if (profile->IsIncognitoProfile() && !profile->IsTor()) {
     return kLastTimeIncognitoUsed;
   }
   return nullptr;
@@ -71,6 +70,16 @@ void BraveWindowTracker::CreateInstance(PrefService* local_state) {
   g_brave_windows_tracker_instance = new BraveWindowTracker(local_state);
 }
 
+bool BraveWindowTracker::HasInstance() {
+  return g_brave_windows_tracker_instance != nullptr;
+}
+
+void BraveWindowTracker::ClearInstance() {
+  CHECK(g_brave_windows_tracker_instance);
+  delete g_brave_windows_tracker_instance;
+  g_brave_windows_tracker_instance = nullptr;
+}
+
 void BraveWindowTracker::RegisterPrefs(PrefRegistrySimple* registry) {
   registry->RegisterTimePref(kLastTimeIncognitoUsed, {});
   registry->RegisterBooleanPref(kTorUsed, false);

browser/p3a/p3a_core_metrics.h

@@ -1,7 +1,7 @@
-/* Copyright 2019 The Brave Authors. All rights reserved.
+/* Copyright (c) 2019 The Brave Authors. All rights reserved.
  * This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
- * You can obtain one at http://mozilla.org/MPL/2.0/. */
+ * You can obtain one at https://mozilla.org/MPL/2.0/. */
 
 #ifndef BRAVE_BROWSER_P3A_P3A_CORE_METRICS_H_
 #define BRAVE_BROWSER_P3A_P3A_CORE_METRICS_H_
@@ -46,6 +46,8 @@ class BraveWindowTracker : public BrowserCollectionObserver {
   ~BraveWindowTracker() override;
 
   static void CreateInstance(PrefService* local_state);
+  static bool HasInstance();
+  static void ClearInstance();
 
   static void RegisterPrefs(PrefRegistrySimple* registry);