Minor cleanup in web_view_browsertest and remove repetitive code.

chrome/test/data/extensions/platform_apps/web_view/download/embedder.js

Index: chrome/test/data/extensions/platform_apps/web_view/download/embedder.js
diff --git a/chrome/test/data/extensions/platform_apps/web_view/download/embedder.js b/chrome/test/data/extensions/platform_apps/web_view/download/embedder.js
index ec4e9b7fd2cfb0319444fa9fb42a730c9196eeeb..db7f9f6e5e23817aa60e1a1c3f6bd5c88b407926 100644
--- a/chrome/test/data/extensions/platform_apps/web_view/download/embedder.js
+++ b/chrome/test/data/extensions/platform_apps/web_view/download/embedder.js
@@ -30,6 +30,13 @@ embedder.setUpGuest_ = function() {
       }
     }
   });
+  var loaded = false;
+  webview.addEventListener('loadstop', function(e) {
+    if (!loaded) {
+      loaded = true;
+      chrome.test.sendMessage('guest-loaded');
+    }
+  });
   return webview;
 };