[Media Router] Add integration browser tests

chrome/test/media_router/media_router_base_browsertest.cc

Index: chrome/test/media_router/media_router_base_browsertest.cc
diff --git a/chrome/test/media_router/media_router_base_browsertest.cc b/chrome/test/media_router/media_router_base_browsertest.cc
index c482015ebbd543f3f76ec7f85b94cc2ca00e4156..08648a3b3de28a5ad766268d5487d074f8c5debc 100644
--- a/chrome/test/media_router/media_router_base_browsertest.cc
+++ b/chrome/test/media_router/media_router_base_browsertest.cc
@@ -67,6 +67,14 @@ void MediaRouterBaseBrowserTest::TearDownOnMainThread() {
   ExtensionBrowserTest::TearDownOnMainThread();
 }
 
+Browser* MediaRouterBaseBrowserTest::GetIncognitoBrowserWithMRExtension() {
+  extension_load_event_.Reset();
+  LoadExtensionIncognito(extension_unpacked_);

[mark a. foltz, 2017/01/20 19:00:09]

What if is_unpacked() == false?

+  extension_load_event_.Wait();
+
+  return CreateIncognitoBrowser();
+}
+
 void MediaRouterBaseBrowserTest::InstallAndEnableMRExtension() {
   if (is_unpacked()) {
     const extensions::Extension* extension = LoadExtension(extension_unpacked_);