Chromecast: disables WebKit's overlay play controls.

R=lcwu@chromium.org,byungchul@chromium.org
BUG=429837

Review URL: https://codereview.chromium.org/687723005

Cr-Commit-Position: refs/heads/master@{#302529}

chromecast/renderer/cast_content_renderer_client.cc

@@ -44,7 +44,11 @@ void CastContentRendererClient::RenderViewCreated(
   blink::WebView* webview = render_view->GetWebView();
   if (webview) {
     webview->setBaseBackgroundColor(kColorBlack);
+
+    // The following settings express consistent behaviors across Cast
+    // embedders, though Android has enabled by default for mobile browsers.
     webview->settings()->setShrinksViewportContentToFit(false);
+    webview->settings()->setMediaControlsOverlayPlayButtonEnabled(false);
   }
 }