[Chromecast] Handle device scale factor correctly

chromecast/browser/test/chromecast_browser_test_helper_default.cc

Index: chromecast/browser/test/chromecast_browser_test_helper_default.cc
diff --git a/chromecast/browser/test/chromecast_browser_test_helper_default.cc b/chromecast/browser/test/chromecast_browser_test_helper_default.cc
index 2c5bf496e7c7d75ef1e61170b088a842b826eb4a..3830fc42ffc82c71fc381237fc2bf98b635d1512 100644
--- a/chromecast/browser/test/chromecast_browser_test_helper_default.cc
+++ b/chromecast/browser/test/chromecast_browser_test_helper_default.cc
@@ -22,11 +22,10 @@ class DefaultHelper : public ChromecastBrowserTestHelper {
 
   content::WebContents* NavigateToURL(const GURL& url) override {
     window_.reset(new CastContentWindow);
-    gfx::Size initial_size(1280, 720);
 
     web_contents_ = window_->CreateWebContents(
-        initial_size, CastBrowserProcess::GetInstance()->browser_context());
-    window_->CreateWindowTree(initial_size, web_contents_.get());
+        CastBrowserProcess::GetInstance()->browser_context());
+    window_->CreateWindowTree(web_contents_.get());
 
     content::WaitForLoadStop(web_contents_.get());
     content::TestNavigationObserver same_tab_observer(web_contents_.get(), 1);