Remove direct uses of TestingFunctionFactory

Replace them with uses of TestingFactory which is based
on base::Callback<> instead of function pointers.

This converts uses in /chrome/browser/extensions/api/mdns.

This CL was uploaded by git cl split.

TBR=vitalybuka@chromium.org

Bug: 809610
Change-Id: I8796684bd7f2948bcf7463a804698aa148a2cfcb
Reviewed-on: https://chromium-review.googlesource.com/c/1246171Reviewed-by: Sylvain Defresne <sdefresne@chromium.org>
Reviewed-by: Vitaly Buka <vitalybuka@google.com>
Commit-Queue: Sylvain Defresne <sdefresne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#596191}

chrome/browser/extensions/api/mdns/mdns_api_unittest.cc

@@ -10,6 +10,7 @@
 #include <utility>
 #include <vector>
 
+#include "base/bind.h"
 #include "base/values.h"
 #include "chrome/browser/extensions/extension_service.h"
 #include "chrome/browser/extensions/extension_service_test_base.h"
@@ -198,9 +199,8 @@ class MDnsAPITest : public extensions::ExtensionServiceTestBase {
   }
 
   // Returns the mDNS API factory function (mock vs. real) to use for the test.
-  virtual BrowserContextKeyedServiceFactory::TestingFactoryFunction
-  GetMDnsFactory() {
-    return MDnsAPITestingFactoryFunction;
+  virtual BrowserContextKeyedServiceFactory::TestingFactory GetMDnsFactory() {
+    return base::BindRepeating(&MDnsAPITestingFactoryFunction);
   }
 
   void TearDown() override {
@@ -257,9 +257,8 @@ class MDnsAPIMaxServicesTest : public MDnsAPITest {
 
 class MDnsAPIDiscoveryTest : public MDnsAPITest {
  public:
-  BrowserContextKeyedServiceFactory::TestingFactoryFunction GetMDnsFactory()
-      override {
-    return MockedMDnsAPITestingFactoryFunction;
+  BrowserContextKeyedServiceFactory::TestingFactory GetMDnsFactory() override {
+    return base::BindRepeating(&MockedMDnsAPITestingFactoryFunction);
   }
 
   void SetUp() override {