[Media Router WebUI] Fix search input and issue overlap.

chrome/browser/resources/media_router/elements/media_router_container/media_router_container.css

Index: chrome/browser/resources/media_router/elements/media_router_container/media_router_container.css
diff --git a/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.css b/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.css
index 62732ef2e8bceac8a77cd3044efe6788557eddc9..05446c29802c02ea9c8e0cf783852ecd7620668e 100644
--- a/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.css
+++ b/chrome/browser/resources/media_router/elements/media_router_container/media_router_container.css
@@ -193,6 +193,10 @@ paper-menu {
   /* TODO(crbug/589697): Handle overflow of very long domain names. */
 }
 
+#sink-list-view {
+  position: relative;
+}
+
 .sink-name {
   min-width: 10%;
   overflow: hidden;