ServiceWorker: Remove iframes explicitly after a test is finished

third_party/WebKit/LayoutTests/http/tests/serviceworker/unregister-then-register.html

Index: third_party/WebKit/LayoutTests/http/tests/serviceworker/unregister-then-register.html
diff --git a/third_party/WebKit/LayoutTests/http/tests/serviceworker/unregister-then-register.html b/third_party/WebKit/LayoutTests/http/tests/serviceworker/unregister-then-register.html
index cec2ddc85410777c300e6c0b14e1fdf958173378..17eeb91609c0120cfe764cdfa7d3e048de2fd49d 100644
--- a/third_party/WebKit/LayoutTests/http/tests/serviceworker/unregister-then-register.html
+++ b/third_party/WebKit/LayoutTests/http/tests/serviceworker/unregister-then-register.html
@@ -39,7 +39,7 @@ async_test(function(t) {
           return wait_for_state(t, r.installing, 'activated');
         })
       .then(function() {
-          return with_iframe(scope);
+          return with_iframe(scope, true);
         })
       .then(function(frame) {
           return registration.unregister();
@@ -68,7 +68,7 @@ async_test(function(t) {
           return wait_for_state(t, r.installing, 'activated');
         })
       .then(function() {
-          return with_iframe(scope);
+          return with_iframe(scope, true);
         })
       .then(function(frame) {
           iframe = frame;
@@ -102,7 +102,7 @@ async_test(function(t) {
           return wait_for_state(t, r.installing, 'activated');
         })
       .then(function() {
-          return with_iframe(scope);
+          return with_iframe(scope, true);
         })
       .then(function(frame) {
           iframe = frame;
@@ -113,7 +113,7 @@ async_test(function(t) {
         })
       .then(function() {
           iframe.remove();
-          return with_iframe(scope);
+          return with_iframe(scope, true);
         })
       .then(function(frame) {
           // FIXME: When crbug.com/400602 is fixed, assert that controller