[Media Router] Reland: MediaRouter interfaces with stub implementations.

chrome/browser/media/router/BUILD.gn

Index: chrome/browser/media/router/BUILD.gn
diff --git a/chrome/browser/media/router/BUILD.gn b/chrome/browser/media/router/BUILD.gn
index 81bc6a87204a90b24e644f05ed720991c3ce647d..746eaa9e3ea1baedd0e2c87c23ef6e79b67cb0e0 100644
--- a/chrome/browser/media/router/BUILD.gn
+++ b/chrome/browser/media/router/BUILD.gn
@@ -6,15 +6,30 @@ import("//testing/test.gni")
 
 source_set("router") {
   deps = [
+    ":router_core",
+    ":keyed_service_factories",
+  ]
+}
+
+source_set("router_core") {
+  deps = [
     "//base",
+    "//components/keyed_service/core",
     "//url",
   ]
   sources = [
     "media_route.cc",
     "media_route.h",
     "media_route_id.h",
+    "media_router.h",
+    "media_router_impl.cc",
+    "media_router_impl.h",
+    "media_routes_observer.cc",
+    "media_routes_observer.h",
     "media_sink.cc",
     "media_sink.h",
+    "media_sinks_observer.cc",
+    "media_sinks_observer.h",
     "media_source.cc",
     "media_source.h",
     "media_source_helper.cc",
@@ -24,10 +39,21 @@ source_set("router") {
   ]
 }
 
+source_set("keyed_service_factories") {
+  deps = [
+    ":router_core",
+    "//components/keyed_service/content",
+  ]
+  sources = [
+    "media_router_impl_factory.cc",
+    "media_router_impl_factory.h",
+  ]
+}
+
 source_set("unit_tests") {
   testonly = true
   deps = [
-    ":router",
+    ":router_core",
     "//base/test:test_support",
     "//testing/gmock",
     "//testing/gtest",