[Chromecast] Add CastMediaBlocker and BrowserTest

chromecast/browser/BUILD.gn

Index: chromecast/browser/BUILD.gn
diff --git a/chromecast/browser/BUILD.gn b/chromecast/browser/BUILD.gn
index c417a42dc2d920f97e58d4e5fcdd5dffcb8907dc..6d0c0369dbffb2d31e80b6e158dec78bc472b37a 100644
--- a/chromecast/browser/BUILD.gn
+++ b/chromecast/browser/BUILD.gn
@@ -30,6 +30,8 @@ source_set("browser") {
     "cast_download_manager_delegate.h",
     "cast_http_user_agent_settings.cc",
     "cast_http_user_agent_settings.h",
+    "cast_media_blocker.cc",
+    "cast_media_blocker.h",
     "cast_net_log.cc",
     "cast_net_log.h",
     "cast_network_delegate.cc",
@@ -179,6 +181,7 @@ config("browser_test_config") {
 test("cast_shell_browser_test") {
   sources = [
     "test/chromecast_shell_browser_test.cc",
+    "test/chromecast_shell_media_blocking_browser_test.cc",
   ]
 
   configs += [ ":browser_test_config" ]