Fix the singleton in ConsentAuditorFactory

ConsentAuditorFactory used CR_DEFINE_STATIC_LOCAL to define a singleton.
In single-process tests, this results in the factory surviving between
subsequent test runs.

Instead, use base::Singleton which is destroyed and recreated with the
test fixture.

Bug: 781765
Change-Id: I46374d6c28ece58eec764db3ff4fa5cffd43216b
Reviewed-on: https://chromium-review.googlesource.com/897947Reviewed-by: Balazs Engedy <engedy@chromium.org>
Commit-Queue: Martin Šrámek <msramek@chromium.org>
Cr-Commit-Position: refs/heads/master@{#533885}

chrome/browser/consent_auditor/consent_auditor_factory.cc

@@ -15,8 +15,7 @@
 
 // static
 ConsentAuditorFactory* ConsentAuditorFactory::GetInstance() {
-  CR_DEFINE_STATIC_LOCAL(ConsentAuditorFactory, factory, ());
-  return &factory;
+  return base::Singleton<ConsentAuditorFactory>::get();
 }
 
 // static

chrome/browser/consent_auditor/consent_auditor_factory.h

@@ -8,6 +8,11 @@
 #include "base/macros.h"
 #include "components/keyed_service/content/browser_context_keyed_service_factory.h"
 
+namespace base {
+template <typename T>
+struct DefaultSingletonTraits;
+}
+
 namespace consent_auditor {
 class ConsentAuditor;
 }
@@ -27,6 +32,8 @@ class ConsentAuditorFactory : public BrowserContextKeyedServiceFactory {
   static consent_auditor::ConsentAuditor* GetForProfile(Profile* profile);
 
  private:
+  friend struct base::DefaultSingletonTraits<ConsentAuditorFactory>;
+
   ConsentAuditorFactory();
   ~ConsentAuditorFactory() override;