Win OS Memory Pressure signals: address some comments from previous CL.

Change-Id: I6625de68dcac33fd74f768d7fa7c60b899e2f200
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2354527
Commit-Queue: Sébastien Marchand <sebmarchand@chromium.org>
Reviewed-by: Rafael Cintron <rafael.cintron@microsoft.com>
Auto-Submit: Sébastien Marchand <sebmarchand@chromium.org>
Cr-Commit-Position: refs/heads/master@{#797936}

base/util/memory_pressure/system_memory_pressure_evaluator_win.cc

@@ -54,22 +54,18 @@ MemoryPressureWatcherDelegate::MemoryPressureWatcherDelegate(
   CHECK(watcher_.StartWatchingOnce(handle_.Get(), this));
 }
 
-MemoryPressureWatcherDelegate::~MemoryPressureWatcherDelegate() {
-  if (watcher_.IsWatching())
-    watcher_.StopWatching();
-  handle_.Close();
-}
+MemoryPressureWatcherDelegate::~MemoryPressureWatcherDelegate() = default;
 
 void MemoryPressureWatcherDelegate::ReplaceWatchedHandleForTesting(
     base::win::ScopedHandle handle) {
   if (watcher_.IsWatching())
     watcher_.StopWatching();
-  handle_.Close();
   handle_ = std::move(handle);
   CHECK(watcher_.StartWatchingOnce(handle_.Get(), this));
 }
 
-void MemoryPressureWatcherDelegate::OnObjectSignaled(HANDLE object) {
+void MemoryPressureWatcherDelegate::OnObjectSignaled(HANDLE handle) {
+  DCHECK_EQ(handle, handle_.Get());
   std::move(callback_).Run();
 }
 
@@ -79,7 +75,8 @@ void MemoryPressureWatcherDelegate::OnObjectSignaled(HANDLE object) {
 // memory pressure monitor. The values were determined experimentally to ensure
 // sufficient responsiveness of the memory pressure subsystem, and minimal
 // overhead.
-const int SystemMemoryPressureEvaluator::kModeratePressureCooldownMs = 10000;
+const base::TimeDelta SystemMemoryPressureEvaluator::kModeratePressureCooldown =
+    base::TimeDelta::FromSeconds(10);
 
 // TODO(chrisha): Explore the following constants further with an experiment.
 
@@ -269,9 +266,8 @@ void SystemMemoryPressureEvaluator::CheckMemoryPressure() {
         // Already in moderate pressure, only notify if sustained over the
         // cooldown period.
         const int kModeratePressureCooldownCycles =
-            kModeratePressureCooldownMs /
-            base::MemoryPressureMonitor::kUMAMemoryPressureLevelPeriod
-                .InMilliseconds();
+            kModeratePressureCooldown /
+            base::MemoryPressureMonitor::kUMAMemoryPressureLevelPeriod;
         if (++moderate_pressure_repeat_count_ ==
             kModeratePressureCooldownCycles) {
           moderate_pressure_repeat_count_ = 0;

base/util/memory_pressure/system_memory_pressure_evaluator_win.h

@@ -33,7 +33,7 @@ class SystemMemoryPressureEvaluator
   // Constants governing the polling and hysteresis behaviour of the observer.
   // The time which should pass between 2 successive moderate memory pressure
   // signals, in milliseconds.
-  static const int kModeratePressureCooldownMs;
+  static const base::TimeDelta kModeratePressureCooldown;
 
   // Constants governing the memory pressure level detection.
 

base/util/memory_pressure/system_memory_pressure_evaluator_win_unittest.cc

@@ -241,9 +241,8 @@ TEST_F(WinSystemMemoryPressureEvaluatorTest, CheckMemoryPressure) {
 
   // Check that the event gets reposted after a while.
   const int kModeratePressureCooldownCycles =
-      evaluator.kModeratePressureCooldownMs /
-      base::MemoryPressureMonitor::kUMAMemoryPressureLevelPeriod
-          .InMilliseconds();
+      evaluator.kModeratePressureCooldown /
+      base::MemoryPressureMonitor::kUMAMemoryPressureLevelPeriod;
 
   for (int i = 0; i < kModeratePressureCooldownCycles; ++i) {
     if (i + 1 == kModeratePressureCooldownCycles) {