[Media Router] Create MediaSinkServiceBase and make DialMediaSinkService inherit from it

chrome/browser/media/router/discovery/BUILD.gn

Index: chrome/browser/media/router/discovery/BUILD.gn
diff --git a/chrome/browser/media/router/discovery/BUILD.gn b/chrome/browser/media/router/discovery/BUILD.gn
index 7b3263f21ea3dde1986443d58ce32bf6799f7b45..946984185f23c36f018b15289ed9e2be107c5e93 100644
--- a/chrome/browser/media/router/discovery/BUILD.gn
+++ b/chrome/browser/media/router/discovery/BUILD.gn
@@ -22,8 +22,8 @@ static_library("discovery") {
     "dial/device_description_service.h",
     "dial/dial_device_data.cc",
     "dial/dial_device_data.h",
-    "dial/dial_media_sink_service.cc",
-    "dial/dial_media_sink_service.h",
+    "dial/dial_media_sink_service_impl.cc",
+    "dial/dial_media_sink_service_impl.h",
     "dial/dial_registry.cc",
     "dial/dial_registry.h",
     "dial/dial_service.cc",
@@ -38,5 +38,7 @@ static_library("discovery") {
     "mdns/dns_sd_device_lister.h",
     "mdns/dns_sd_registry.cc",
     "mdns/dns_sd_registry.h",
+    "media_sink_service_base.cc",
+    "media_sink_service_base.h",
   ]
 }