[Media Router] Add integration browser tests

chrome/test/media_router/media_router_base_browsertest.h

Index: chrome/test/media_router/media_router_base_browsertest.h
diff --git a/chrome/test/media_router/media_router_base_browsertest.h b/chrome/test/media_router/media_router_base_browsertest.h
index cbfc9e52a1da27d8c1d6406069e7c96c3a1257b6..4e903cc4f782ad30f406abf0a1d80f146703e253 100644
--- a/chrome/test/media_router/media_router_base_browsertest.h
+++ b/chrome/test/media_router/media_router_base_browsertest.h
@@ -43,6 +43,10 @@ class MediaRouterBaseBrowserTest : public ExtensionBrowserTest,
   void SetUpOnMainThread() override;
   void TearDownOnMainThread() override;
 
+  // Installs the Media Router extension for the incognito profile and returns
+  // an incognito browser.
+  Browser* GetIncognitoBrowserWithMRExtension();

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

It seems inconsistent for this to return a Browser* while
InstallAndEnableMRExtension() below for normal profiles does not.

[takumif, 2017/02/07 22:17:35]

Making a subclass for incognito.

+
   void InstallAndEnableMRExtension();
   void UninstallMRExtension();