Adopt base::NoDestructor for KeyedService factories

For changes under /chrome/browser/page_load_metrics

It replaces base::Singleton, following the latest recommendation
in base/ and browser_context_keyed_service_factory.h.

For factories with a trivial destructor, it makes no difference.

LSC doc:
https://docs.google.com/document/d/1x1LqRQyfBOmpMkNQBYs7QBPSxLtuiImvmgcJYI_kaS4/edit?usp=sharing

This CL was uploaded by git cl split.

R=sullivan@chromium.org

Bug: 925323
Change-Id: I344e8bc22fc18d79875b7904edc6982a035a218c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/4573384
Auto-Submit: Mikel Astiz <mastiz@chromium.org>
Reviewed-by: Annie Sullivan <sullivan@chromium.org>
Commit-Queue: Annie Sullivan <sullivan@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1150317}

chrome/browser/page_load_metrics/observers/https_engagement_metrics/https_engagement_service_factory.cc

@@ -4,7 +4,7 @@
 
 #include "chrome/browser/page_load_metrics/observers/https_engagement_metrics/https_engagement_service_factory.h"
 
-#include "base/memory/singleton.h"
+#include "base/no_destructor.h"
 #include "chrome/browser/page_load_metrics/observers/https_engagement_metrics/https_engagement_service.h"
 
 // static
@@ -16,7 +16,8 @@ HttpsEngagementService* HttpsEngagementServiceFactory::GetForBrowserContext(
 
 // static
 HttpsEngagementServiceFactory* HttpsEngagementServiceFactory::GetInstance() {
-  return base::Singleton<HttpsEngagementServiceFactory>::get();
+  static base::NoDestructor<HttpsEngagementServiceFactory> instance;
+  return instance.get();
 }
 
 HttpsEngagementServiceFactory::HttpsEngagementServiceFactory()
@@ -29,7 +30,7 @@ HttpsEngagementServiceFactory::HttpsEngagementServiceFactory()
               .WithGuest(ProfileSelection::kRedirectedToOriginal)
               .Build()) {}
 
-HttpsEngagementServiceFactory::~HttpsEngagementServiceFactory() {}
+HttpsEngagementServiceFactory::~HttpsEngagementServiceFactory() = default;
 
 KeyedService* HttpsEngagementServiceFactory::BuildServiceInstanceFor(
     content::BrowserContext* context) const {

chrome/browser/page_load_metrics/observers/https_engagement_metrics/https_engagement_service_factory.h

@@ -13,7 +13,7 @@ class BrowserContext;
 
 namespace base {
 template <typename T>
-struct DefaultSingletonTraits;
+class NoDestructor;
 }
 
 class HttpsEngagementService;
@@ -31,7 +31,7 @@ class HttpsEngagementServiceFactory : public ProfileKeyedServiceFactory {
       const HttpsEngagementServiceFactory&) = delete;
 
  private:
-  friend struct base::DefaultSingletonTraits<HttpsEngagementServiceFactory>;
+  friend base::NoDestructor<HttpsEngagementServiceFactory>;
 
   HttpsEngagementServiceFactory();
   ~HttpsEngagementServiceFactory() override;

chrome/browser/page_load_metrics/page_load_metrics_memory_tracker_factory.cc

@@ -4,7 +4,7 @@
 
 #include "chrome/browser/page_load_metrics/page_load_metrics_memory_tracker_factory.h"
 
-#include "base/memory/singleton.h"
+#include "base/no_destructor.h"
 #include "components/page_load_metrics/browser/page_load_metrics_memory_tracker.h"
 
 namespace page_load_metrics {
@@ -18,7 +18,8 @@ PageLoadMetricsMemoryTrackerFactory::GetForBrowserContext(
 
 PageLoadMetricsMemoryTrackerFactory*
 PageLoadMetricsMemoryTrackerFactory::GetInstance() {
-  return base::Singleton<PageLoadMetricsMemoryTrackerFactory>::get();
+  static base::NoDestructor<PageLoadMetricsMemoryTrackerFactory> instance;
+  return instance.get();
 }
 
 PageLoadMetricsMemoryTrackerFactory::PageLoadMetricsMemoryTrackerFactory()