[mDns] Make DnsSdRegistry a leaky singleton

chrome/browser/extensions/api/mdns/mdns_api.h

Index: chrome/browser/extensions/api/mdns/mdns_api.h
diff --git a/chrome/browser/extensions/api/mdns/mdns_api.h b/chrome/browser/extensions/api/mdns/mdns_api.h
index d5b4e051501211c0be9b2ca946736c19b0c085b2..32a6e706cab30fdea1c3bd8c3c310c53ab1c4f04 100644
--- a/chrome/browser/extensions/api/mdns/mdns_api.h
+++ b/chrome/browser/extensions/api/mdns/mdns_api.h
@@ -45,9 +45,9 @@ class MDnsAPI : public BrowserContextKeyedAPI,
   // BrowserContextKeyedAPI implementation.
   static BrowserContextKeyedAPIFactory<MDnsAPI>* GetFactoryInstance();
 
-  // Used to mock out the DnsSdRegistry for testing.
-  void SetDnsSdRegistryForTesting(
-      std::unique_ptr<media_router::DnsSdRegistry> registry);
+  // Used to mock out the DnsSdRegistry for testing. Does not take ownership of
+  // |registry|.
+  void SetDnsSdRegistryForTesting(media_router::DnsSdRegistry* registry);
 
   // Immediately issues a multicast DNS query for all service types.
   // NOTE: Discovery queries are sent to all event handlers associated with
@@ -112,8 +112,9 @@ class MDnsAPI : public BrowserContextKeyedAPI,
   // Ensure methods are only called on UI thread.
   base::ThreadChecker thread_checker_;
   content::BrowserContext* const browser_context_;
-  // Lazily created on first access and destroyed with this API class.
-  std::unique_ptr<media_router::DnsSdRegistry> dns_sd_registry_;
+  // Raw pointer to a leaky singleton. Lazily created on first access. Must
+  // outlive this object.
+  media_router::DnsSdRegistry* dns_sd_registry_;
   // Count of active listeners per service type, saved from the previous
   // invocation of UpdateMDnsListeners().
   ServiceTypeCounts prev_service_counts_;