Make ctor explicit and factory dtor virtual in CryptAuthKeyRegistryImpl

Note: The C++ style guide states, "Type conversion operators, and
constructors that are callable with a single argument, must be marked
explicit in the class definition."

Bug: 899080
Change-Id: I013f807d451fd540190dbd8f06b1977a83b6b013
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1521280
Commit-Queue: Josh Nohle <nohle@chromium.org>
Reviewed-by: Kyle Horimoto <khorimoto@chromium.org>
Auto-Submit: Josh Nohle <nohle@chromium.org>
Cr-Commit-Position: refs/heads/master@{#642351}

chromeos/services/device_sync/cryptauth_key_registry_impl.cc

@@ -33,6 +33,8 @@ void CryptAuthKeyRegistryImpl::Factory::SetFactoryForTesting(
   test_factory_ = test_factory;
 }
 
+CryptAuthKeyRegistryImpl::Factory::~Factory() = default;
+
 std::unique_ptr<CryptAuthKeyRegistry>
 CryptAuthKeyRegistryImpl::Factory::BuildInstance(PrefService* pref_service) {
   return base::WrapUnique(new CryptAuthKeyRegistryImpl(pref_service));

chromeos/services/device_sync/cryptauth_key_registry_impl.h

@@ -26,6 +26,7 @@ class CryptAuthKeyRegistryImpl : public CryptAuthKeyRegistry {
    public:
     static Factory* Get();
     static void SetFactoryForTesting(Factory* test_factory);
+    virtual ~Factory();
     virtual std::unique_ptr<CryptAuthKeyRegistry> BuildInstance(
         PrefService* pref_service);
 
@@ -41,7 +42,7 @@ class CryptAuthKeyRegistryImpl : public CryptAuthKeyRegistry {
  private:
   // Populates the in-memory key bundle map with the enrolled key bundles
   // persisted in a pref.
-  CryptAuthKeyRegistryImpl(PrefService* pref_service);
+  explicit CryptAuthKeyRegistryImpl(PrefService* pref_service);
 
   // CryptAuthKeyRegistry:
   void OnKeyRegistryUpdated() override;