Add Media Router Mojo impl code.

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 6ee9a6f893756b1f8f9e09d961c98b9dac500fef..c0bebee53f9023f1ab474bfd568c4450d51ba80f 100644
--- a/chrome/browser/media/router/BUILD.gn
+++ b/chrome/browser/media/router/BUILD.gn
@@ -8,6 +8,7 @@ import("//third_party/mojo/src/mojo/public/tools/bindings/mojom.gni")
 source_set("router") {
   deps = [
     ":router_core",
+    ":keyed_service_factories",
   ]
 }
 
@@ -31,6 +32,8 @@ source_set("router_core") {
     "media_route.h",
     "media_route_id.h",
     "media_router.h",
+    "media_router_mojo_impl.cc",
+    "media_router_mojo_impl.h",
     "media_router_type_converters.cc",
     "media_router_type_converters.h",
     "media_routes_observer.cc",
@@ -50,6 +53,17 @@ source_set("router_core") {
   ]
 }
 
+source_set("keyed_service_factories") {
+  deps = [
+    ":router_core",
+    "//components/keyed_service/content",
+  ]
+  sources = [
+    "media_router_mojo_impl_factory.cc",
+    "media_router_mojo_impl_factory.h",
+  ]
+}
+
 source_set("unit_tests") {
   testonly = true
   deps = [