Remove unwanted <webview> border in OOPIF mode.

extensions/renderer/resources/guest_view/guest_view_iframe_container.js

Index: extensions/renderer/resources/guest_view/guest_view_iframe_container.js
diff --git a/extensions/renderer/resources/guest_view/guest_view_iframe_container.js b/extensions/renderer/resources/guest_view/guest_view_iframe_container.js
index 4cd628be8f7ca6aa6791d45cc914e885dc7be89a..eb04cca2a843df8d560473535899f2b3bf88da97 100644
--- a/extensions/renderer/resources/guest_view/guest_view_iframe_container.js
+++ b/extensions/renderer/resources/guest_view/guest_view_iframe_container.js
@@ -11,6 +11,7 @@ GuestViewContainer.prototype.createInternalElement$ = function() {
   var iframeElement = document.createElement('iframe');
   iframeElement.style.width = '100%';
   iframeElement.style.height = '100%';
+  iframeElement.style.border = '0';
   privates(iframeElement).internal = this;
   return iframeElement;
 };