Update the build rule for media router tests (e2e) and the mapping.

chrome/test/media_router/BUILD.gn

Index: chrome/test/media_router/BUILD.gn
diff --git a/chrome/test/media_router/BUILD.gn b/chrome/test/media_router/BUILD.gn
index c82bd8ab4dccb130afcfc336a1b2f22121ce4856..15df18ec870e6e2cee810fcf16c113101e23a509 100644
--- a/chrome/test/media_router/BUILD.gn
+++ b/chrome/test/media_router/BUILD.gn
@@ -2,6 +2,19 @@
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+group("media_router_tests") {
+  testonly = true
+  data_deps = [
+    "//chrome/test:browser_tests",
+  ]
+  data = [
+    "$root_out_dir/mr_extension/",
+    "internal/",
+    "../../../media/test/data/player.html",
+    "../../../media/test/data/bear-vp9-opus.webm",
+  ]
+}
+
 # Browser test resource files.
 media_router_integration_test_resources = [
   "resources/basic_test.html",